Joao S. Lopes wrote (N.B. I have slightly edited the text of his post):
> [Could <fla:men> come from older <*fra:men>, modified through
> influence of flamma?]
I think one should analyse, in the first place, the Latin-Messapic (Illyrian?) isogloss <fla:men> :: <blamini> 'priest'.
Latin <fla:men> seems to be an older neuter indicating the performance of the sacrifice, which makes the connection with Proto-Germanic *blo:tan- 'sacrifice' likely.
Sophus Bugge suggested in the late 19th century that <fla:men> is from an older *fla:d-men < PIE *bhla:d(-s)-men 'sacrificer'.
Messapic <blamini> too may have derived from PIE *bhla:d(-s)-men (?).
As to Proto-Germanic *blo:tan, it can easily be derived from a PIE verbal stem *bhla:d- 'to sacrifice'.
Regards,
Francesco