late 14c., from Old French rumor "commotion, widespread noise or report" (Modern French rumeur), from Latin rumorem (nominative rumor) "noise, clamor, common talk, hearsay, popular opinion," related to ravus "hoarse," from PIE *reu- "to bellow." Related: Rumorous. Rumor mill is from 1887. Dutch rumoer, German Rumor are from French.
1590s, "spread a rumor; spread by way of rumor," from rumor (n.). Related: Rumored; rumoring.