c. 1600, with -al (1) + Late Latin aequivocus "of identical sound, of equal voice, of equal significance, ambiguous, of like sound," past participle of aequivocare, from aequus "equal" (see equal (adj.)) + vocare "to call," which is related to vox (genitive vocis) "voice" (from PIE root *wekw- "to speak"). Earlier in same sense was equivoque (late 14c.). Related: Equivocally (1570s).