French, literally "in passing," from present participle of passer "to pass" (see pass (v.)). In reference to chess, first attested 1818.
Entries linking to en passant
late 13c., passen (transitive), "to go by (something)," also "to cross over," from Old French passer "to pass" (11c.), from Vulgar Latin *passare "to step, walk, pass" (source also of Spanish pasar, Italian passare), from Latin passus "step, pace" (from PIE root *pete- "to spread").
Intransitive sense of "to go on, to move forward, make one's way" is attested from c. 1300. The figurative sense of "to experience, undergo" (as in pass the time) is recorded from late 14c. Sense of "to go through an examination successfully" is from early 15c. Meaning "decline to do something" is attested from 1869, originally in cards (euchre). In football, hockey, soccer, etc., the meaning "to transfer the ball or puck to another player" is from c. 1865. Related: Passed; passing.
The meaning "to be thought to be something one is not" (especially in a racial sense) is from 1935, from pass oneself off(as), which is attested by 1809. The general verb sense of "to be accepted as equivalent" is from 1590s. Pass up "decline, refuse" is attested from 1896. Pass the buck is from 1865, said to be poker slang reference to the buck horn-handled knife that was passed around to signify whose turn it was to deal. Pass the hat "seek contributions" is from 1762. Pass-fail as a grading method is attested from 1955, American English.