I am currently reading ‘Y Llythyr’ (one of the new Amdani series, good read) and came across this description of a father meeting his long-lost daughter: ‘Cymerodd e ei dwy law yn ei ddwylo’. So would I be right in thinking that it’s ‘dwy law’ when the hands are conceived of as being apart, but ‘dwylo’ when they are being conceived of as a pair together? Thus you would catch a ball in ‘dwylo’ but play the piano with ‘dwy law’? Or is it not that simple?
Dwylo is the plural of llaw. And, yes, it is derived from dwy law. There is, of course a subtle difference conceptually between her two hands and his hands.
I think what may be happening here is that you’ve spotted that there is (as far as I know) no literal Welsh equivalent to an English phrase such as he took her hands in his, where the second hands is assumed, so the writer has to be creative in order to avoid clumsy repetition.
I think that is spot-on, @Davids - dwylo is indeed (as you suggest) the collective for the pair, so for this most common use it is the plural - but there is a ‘regular’ plural llawiau which you get when NOT talking about a pair of hands:
Mae’r bobol 'ma’n hen lawiau ar drefnu ymgyrchoedd
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