Never mind, Gareth bach!
Given the amount that you transcribe no-one could reasonably complain!
And I was probably just being a bit of a tease, too! (My late mother always
said it would be my undoing).
And neither of the dictionaries I usually use were much use, either (Gareth
King, 'Oxford Modern' --- brilliant though it is for most purposes and Evans
and Thomas, 'Y Geiriadur Newydd'--- old-fashioned, but more complete).
However, my Thomas Jones 'Geiriadur Saesonaeg [sic] a Chymraeg', Clwydian
Press, 1826, has for 'faithful' -- ffyddlawn.
And for 'faithfulness'--- 'ffyddolendeb'. So it looks like
mutated towards 'ffyddlon' over the last two centuries.
Thanks David, and Tudor off list, it would seem likely to be an archaic
version of ffyddlon.
Neither of the dictionaries I use has it.
BTW, I can't remember what I transcribed last week, never mind a couple of
months ago :-)