What is the X in X-mas?
late 14c., "spoken, oral," from Old French vocal, from Latin vocalis "sounding, sonorous, speaking," as a noun, "a vowel," from vox (genitive vocis) "voice" (see voice (n.)). In reference to music (as opposed to instrumental), first recorded 1580s; meaning "outspoken" first attested 1871. Vocal cords is from 1872; see cord.
vocal vo·cal (vō'kəl)
Of or relating to the voice.
Capable of emitting sound or speech.