From the experts:
A favorite of British novelists including Evelyn Waugh and P. G. Wodehouse, Ambrose has an air of blooming well-being and upper-class erudition. It comes from the same Greek root as 'ambrosia', the food of the gods, literally 'belonging to the immortals.'
Ambrose was the name of one of the important doctors of the early Christian church, the fourth century St. Ambrose. It also belonged to one of the four great Latin teachers of Christianity, who also developed the use of music in church services. TV fanatics might be interested to know that in 1961, Ambrose was designated the patron saint of educational television by Pope John XXII.
Ambrose's only problem is finding a nickname--aside from the all too obvious Rosie.