English
foamer
From foam + -er.
Formed from foam + -er
Proto-Indo-European *(s)poH(y)-
…
Proto-Germanic *faimaz
Proto-West Germanic *faim ‘foam, froth’
Old English fām
Middle English fom
English foam
The story
Foamers are called so because they foam at the mouth with awe
Today it means
noun A railfan, particularly an obsessive one.
Language periods are conventional ranges, not dates for this word.
Etymograph / foamer