Old English steam "vapor, fume," from Proto-Germanic *staumaz (cf. Dutch stoom), of unknown origin. Steam age first attested 1941. Steam heat as a method of temperature control recorded from 1904.
Old English stemen, stymen "to emit a scent or odor," from the root of steam (n.). Slang meaning "to make angry" is from 1922. Related: Steamed; steaming.
To talk loudly and angrily as a method of relieving the pressure of one's feelings; express one's anger or frustration: He's not serious, just letting off steam/ I've blown off steam/ They're bored, just blowing off steam (1837+)