Hi Mona,
> "bauen", but that one is (or became?) a weak verb in german.
Originally it was Class VII strong verb, that's to say it had a past
tense formed by reduplication like róa 'to row', reri 'rowed'. In
Icelandic this is obscured a bit since the initial consonant of the
root was dropped by dissimilation, so: *bebú > *beú > bjó.
In Gothic bauan has a weak past tense, but the old strong endings
remain in the present. In OHG bûan is already weak.
Llama Nom