early 15c., "sundial," earlier "dial of a compass" (mid-14c.), apparently from Medieval Latin dialis "daily," from Latin dies "day" (see diurnal).The word perhaps was abstracted from a phrase such as Medieval Latin rota dialis "daily wheel," and evolved to mean any round plate over which something rotates. Telephone sense is from 1879, which led to dial tone (1921), "the signal to begin dialing," which term soon might be the sole relic of the rotary phone.

1650s, "to work with aid of a dial or compass," from dial, n.. Telephone sense is from 1923. Related: Dialed; dialing.