Ade wrote:
fo/fu/fa is the historical form of this preposition. It seems it's rarely (if ever) found written with a mark of length in Old Irish sources (see
eDIL), but that the mark of length became more common in Middle Irish manuscripts like
Lebor na hUidre. That's not to say that it definitely wasn't pronounced with a long vowel, as marks of length are often omitted in Old Irish manuscripts, but the apparent total lack of accent marks in Old Irish sources combined with the variation in spelling (
fo/fu/fa) makes me suspect the vowel was probably pronounced something closer to ə originally.
Base prepositions were generally unstressed (hence today
ag before verbal nouns and
ar in some set phrases like
ar bith are pronounced as /ə(ɡ), ə(r)/). Old Irish in pretonic position had three short phonemic vowel qualities, typically transcribed /a, o, i/ (hence eg. deuterotonic
·epir changes to prototonic
as·beir, both from *
exs-beret(i) – there was no pretonic /e/). So
fo and
fu would be just two ways of writing pretonic /ɸo/. And I suspect the actual vowel was some kind of rounded mid-vowel, like rounded schwa [ə̹], or maybe [ɵ], rather than actual [o] or [u].
fa would be Middle Irish reduction of all short unstressed vowels to schwa, /ɸə/.
The forms
faoi, fé of course continue the 3rd person masculine sg. form of the preposition, cf.
ag,
ar being normally pronounced /eɡ´(ɪ) ~ ɪˈɡ´e, er´/ under influence of the inflected 3rd sg. m. forms
aige, air, or
go, chuige changing into separate things and new base form
chuig appearing in the north (while in Munster
chuige getting associated with
do-chum, chun).
Also, from random things related to this, worth noting that
ó thuaidh ‘northwards’ and
ó dheas ‘southwards’ continue OIr.
fo·thúaid and
fo·dess with this very preposition (and
siar, soir, suas, etc. might also have its other form, the preposition being *(s)upo in PIE > *(s)uo > *(s)wo > OIr.
fo / *so, with
*so perhaps kept as
*s- prefixed to vowel-initial words?).