Well, aye- in the same way that Welsh emulated (maybe) French etc. But that did mean that it became such a natural part of the language that the “thou” form was lost.
It may have been initially taken from outside influences (as a lot of grammar and words are) but it had to become a natural part of the language before people used it to such an extent that “thou” was lost in normal conversation!
When my family moved to York in the 50’s, I was asked, “Wha’d’they call thee?” It took some time for me to work out that I was being asked my name. I lived in Yorks briefly in early 70’s and I think ‘thee’ was still used then.
That’s not how I see it. The way I see it is because it was not a natural part of the language, there was not a good sense on when to use thou and when to use you. The popularity of using you as a polite form led to thou being distasteful which led people to stop using it. If it were a natural part of the language this would likely not have happened. But of course I wasn’t there, so who really knows. 
Oh, whether it was originally part of the language would have had an effect on the use of the word, certainly!
Such usage was taken into Welsh as well as English.
Welsh seems to be reverting back to a “chi” solely meaning plural usage, whereas in English “you” replaced “thou”. The reasons behind theses changes are so complicated as to be impossible to be sure about, as we weren’t there, as you say!
And even if the use came about internally, and not from outside usage, the use of it would surely change over time in an unpredictable way, as all such things do, of course!
As you say, it is impossible to be certain without a long life and a time machine
[edit- looking at this more carefully, I think it comes down to the definition of the word “natural”, which can mean an awful lot of different things. A lot of apparent differences in opinion are down to the definitions of words!]
There is a nice (but probably apocryphal) story of a young apprentice (perhaps in the 19th century) somewhere “oop north” who dared to address his foreman as “thou”, to which he got the reply:
“Don’t thee thou me. Thee thou them as tha’s thee!”
There are various versions on this on the web, but I first heard it as above from my Lancastrian (Preston) father-in-law (born 1917).
As has been referred to, Yorkshire is, or was, well known for preserving “thou” (pronounced “tha”), and “thee” for the object form, but it was probably a general northern thing at one time, e.g. Derbyshire as has been mentioned, and I myself heard rural people in north Lancashire / southern Cumbria using it, back in the 60s or so. e.g. “How’s tha doin’ lad?” “Aal reet and how’s tha?”
I have a dim childhood recollection that this also applied in Welsh when addressing a person of distiction or even a revered grandparent. Can any Welsh speakers of a certain age confirm this?
and they take the same form of the verb e.g.
Sie schliessen (*versus du schliesst) and sie schliessen.???
So how do you know when what is being said between:
they close - sie schliessen
and
you close - sie schliessen
Is it by context???
Justin
You see my trip to Austria was not totally wasted!!
Hi Tatjana,
I’m so glad you brought this up because I realize, as a babe in the woods, learning Germanh that I’m not sure when to use Sie, sie and Ihr because Ihr is another form of you - isn’t it e.g. Ihr seid (you are)??
Justin
Hey! Du lernst, sehe ich. 
(not even a bit grammatically correct sentence but I like to play with words this way sometimes).
Well, inbetween Sie and sie it’s real difference only in writing and not in speach though. All is about the context in speach, yes. However when writing capitals are very important and if you’ve noticed, all nouns are written with capitals.
Ihr is even more polite form, yes and is also used in both way, plural and singular. And ihr is also used in sentences like "Sagen sie mir Ihren Namen bitte.
But, to be honest I’m not too big grammatical geek also. Articles are most common difficulties especially as you have to know for each and every noun what gender it is in order to lean of the nouns. Even Germans (as far as I’ve heard) have difficulties with this though.
And, yes, I’m glad your trip to Austria was of some language value aswell. Next year you’ll speak German as I sit here. They we could talk some too.
I’m in Paris today and just met a very interesting Croatian. He tried to convince me to learn Croatian. Do you speak Croatian?
Do Slovenians understand Croations?
Do Croatians understand Russians and vice versa?
Justin
I speak Serbo-Croatian what is really little difference from pure Croatian so I’d say yes.
Why not? Try and you’ll see how ti goes. I can’t actually really say if would be hard for you or not since I’m keen to it and might not assess is it difficult or not to learn. Well basically it’s quite similar to Slovene (despite it doesn’t have duality what is big +).
We, Slovenians (well mostly older generations though) understand Croatians by nature as we lived long years in common country and we even today speak Serbo-Croatian, Croatian or Serbian a lot. So, yes, we understand Croatians and vice versa.
Russian is already a bit different from all our three languages - Croatian, Serbian and Slovenian, but we surely would quite understand each others at least in some parts. There’s still Russian taught in Serbia as foreign language at least in middle schools if I’m correct.
You surely already learnt some tinny bits of it, didn’t you?
Not even a tiny bit of Croatian was spoken unfortunately. My Croatian friend was totally focussed on practicing his French and English.
Thinking about all this, I think I’ll attempt to learn Russian first and then try to bridge to learning Croatian if I have still some energy left!!
Justin
Yes, context. In practice there is rarely a problem.
Written formal “you” is usually written with a capital S - Sie.
“Ihr” in this context is the plural familiar form of “you”, i.e. the plural of “du”.
(“du” used to be written with capital D in correspondence, but often isn’t now).
The word “ihr” has some other uses, but in those, it does not mean “you”, so I won’t complicate matters here.
One of the fun things in German is that pronouns change according to the way they are used, or in grammatical terms, according to the case, and also to the gender, of which there are three in German.
It’s a bit like the articles, der, die das, but slightly more irregular (just to add to the fun).
the best way to learn them would be the SSi way, which is essentially the way that Germans learned them, because no normal human being can carry around the declension table in their head and use it in real time to make conversation. If you try to, it obviously slows you down…
(as I know to my cost!)
Yay! @JustinandEirwen ths is fun! You’ve just got yourself more experienced tutor then I am. I didn’t speak German (except for that conversation once with @brigitte) for about 10 or even more years and I didn’t write it even longer periode …
For the record, I’m reviving some of my knowledge with Memrise with one course which teaches you verbs and with one which teaches you nouns (and what’s more to it) with articles. I could establish that I still know more then I forgot what is challengly exciting though. I am really curious if (perhaps) Italian and/or German comes to SSi, how I’d do. But (kind of sadly) probably better then Cymraeg.
(ups … we’ve sailed so much off topic … but it’s exciting though)
Thanks for the tips on learning German. That’s great - I’m a little less confused.
Yes,I will be trying to learn the SSi way
Because August is so hot by the Mediterranean, I’m planning to flee to the Austrian hills each year for a few weeks each Summer. My landlady there has promised to speak German with me. So I’m excited that I’ve got a route into speaking German,
Justin
One nice thing about German is that there are tons of podcasts out there, lots from the various public broadcasters, some private ones, and lots of stuff on Deutsche Welle, the German Overseas Service (which broadcasts in many languages, not just German). Not sure if there are many transcripts available, but DW has some for its more learner-oriented material.
You could say that this is passive learning and not speaking, but at least it will offer very good learning comprehension exercise and vocabulary-stretching, and training your ear for accents, and a bonus with German is that, especially with the public radio podcasts, they speak nice and clearly, so at least you can hear every word (usually), which is half the battle.
Under one condition. The ending greeting (if it’s the same place as you were this summer) is in Slovene. - hehe
(Just (partly) kidding)
Well, @mikeellwood, my ears are very well trained to “not clear” German as I had to deal with one man from Schwabeland who didn’t even want to speak clear German so clear one is bonus for me though.
I don’t need to go far to listen to German speach though. Our national Radio-Television has one radio station of Radio Maribor called MM2 and the program is only in German language. And … we’re not far from Austrian border either. The fact is that you could quite often hear more tourists speaking German then English aswell. But still, it’s not problem to talk German to me but to write, I rather escape to English when I have to send some invoices back to German partners of the company in which I work.
Ja … so ist die Geschichte …
Yes, in writing, you really cannot escape the grammar!
No question that the German dialects are difficult, but of course, almost all the public broadcasts are in Hochdeutsch.
How do they know that I am using CAPITALS correctly when I am just talking!! So you see the SSi approachto learning a language is by leaps and bounds superior - and easier, too!
Justin
Oooo, yes. Here I jsut have to agree …