It seems that the 'Offa' of Mercia, whose origins are obscure, may well have been born with an entirely different name and that Offa was rather his adopted name, chosen one must presume, because it had some significance to the Mercians of the time.
It may possibly have been a harking back to the legendary king Offa of the Angles, but the name Offa also means in Latin a 'ball of dough', which may have had some concious religious symbolism and an attempt by the Mercian Offa to portray himself as some kind of
redeemer king.