The Collaborative International Dictionary
Pneumo-
Pneumo- \Pneu"mo-\ A combining form from Gr. ?, ?, a lung; as, pneumogastric, pneumology.
Douglas Harper's Etymology Dictionary
pneumo-
before vowels pneum-, word-forming element meaning "lung," from comb. form of Greek pneumon (see pneumonia).
Wiktionary
pneumo-
pre. '''pneum-''' + '''-o-'''