Why is the ninth month called September?
late 14c. (implied in tripper), "tread or step lightly, skip, caper," from Old French tripper "strike with the feet" (12c.), from a Germanic source (cf. Middle Dutch trippen "to skip, trip, hop," Low German trippeln, Frisian tripje, Dutch trappen, Old English treppan "to tread, trample") related to trap.
The sense of "strike with the foot and cause to stumble" is first recorded early 15c. Meaning "to release" (a catch, lever, etc.) is recorded from 1897; trip-wire is attested from 1916. Related: Tripped; tripping.
"act or action of tripping," 1650s, from trip (v.); sense of "a short journey or voyage" is from 1690s, originally a nautical term, the connection is uncertain. The meaning "psychedelic drug experience" is first recorded 1959 as a noun; the verb in this sense is from 1966, from the noun.
An arrest; a prison sentence; fall
[1920s+ Underworld; fr trip, ''stumble, fall'']