The vowel exchange "a" to "o"

[Mauro]

Do you know a language or old manuscripts in which a vowel exchange with always the same two vowels is typical or at least known or occurs?

'Known to occour'? Standard Italian:

caso (case), casa (house), case (houses) cosa (thing), coso (thing), cose (things), cosi (things)...
raso (shaved + another couple meanings), rosa (rose, pink), roso (gnawed), reso (returned), resa (returned), risa (laughters)....
razza (race), razzo (rocket), rozzo (rough)
pazza (madwoman), pazzo (madman), pozzo (well), pozza (puddle), pizza, pezza, puzza.....
..... .... .....

And more generally,+- every feminine noun/adjective etc. ending in 'a' has a male counterpart ending in 'o', while at the plural the endings are replaced by 'e' (feminine) and 'i' (male). So I guess one can say Standard Italian 'exchanges' a lot of vowels.