"instrument for measuring the interference of light waves," 1897, a hybrid from interfere + -meter. Compare interferential (1867), coined on the model of differential. Related: Interferometric; interferometry.
formerly also enterfere, mid-15c., enterferen, "intermingle or mix (different things), interpose," also "to interfere," from Old French enterferer "exchange blows, strike each other," from entre- "between" (see entre-) + ferir "to strike," from Latin ferire "to knock, strike," related to Latin forare "to bore, pierce" (from PIE root *bhorh- "hole"). Compare punch (v.), which has both the senses "to hit" and "to make a hole in").
Figurative sense of "to meddle with, oppose unrightfully" is from 1630s. Related: Interfered; interfering. Modern French interférer is from English.