Some of the words from "Is Iomaí Duine ag Dia" ending in 'acán/agán'
are related to adjectives ending in '-ach' with similar meanings.
guagach - guagán
spágach - spágán
lomrach - lomracán
stuacach - stuacán
éagach - éagán
Dinneen has "lámhach ready-handed, dexterous"
also "lámhachán a masculine substantive "creeping on hands and feet"
and "lámhachánaidhe one who creeps on hands and knees"
Dinneen translates 'leabhrach' as "bookish; having many books". He
doesn't specifically say that it refers to a person (rather than a thing
with a lot of books), but it sounds like a person to me.
FGB translates it simply "bookish"
Could 'leabhragán' have come from the adjective 'leabhrach'? Liz