Francine Nicholson wrote:

> But my question remains: what meaning did cruimther have in
> Old Irish to distinguish it from sacart?

I'm not aware of any difference in meaning.  I suppose
there could have been some technical distinction, but
they may have differed mainly in peripheral 'flavour'.
I my own English, 'pastor' and 'minister' are nearly
identical in meaning, as are 'doctor' and 'physician'
in most contexts.

It looks to me as if 'cruimther' is mainly a case of
FIFO: first in, first out.  The /p/ to /kw/ phonological
thing points to its early arrival, and this is reinforced
by the evidence of the ogam inscription


in which the first word is the equivalent of 'cruimthir',
the genitive of 'cruimther'.  Yet the word has left no
trace in Modern Irish, outside of placenames, as far as
I know.  'Sacart' endures and may have gained the upper
hand for any number of reasons -- perhaps simply because
it sounded nicer?  It is pronounced the same today as it
was when it appearance in the OI Glosses, while 'cruimther'
underwent several changes, finally ending up spelled
'crumper', 'cruimpir', etc.

Incidentally, if "cruimther" were to be reintroduced from
OI into today's language, it would be spelled "cruimhthear",
and I'd pronounce it something like 'kriffer' /krif’@r/!