late 14c., entunen "sing, chant, recite," from Old French entoner "sing, chant" (13c.), from Medieval Latin intonare "sing according to tone," from Latin in- "in" (see in-(2)) + tonus "tone," from Greek tonos (see tenet). A different verb intone was in use 17c.18c., from Latin intonare "to thunder, resound," figuratively "to cry out vehemently," from tonare "to thunder." Related: Intoned; intoning.