holler (v.)

1690s, American English, variant of hollo (1540s) "to shout," especially "to call to the hounds in hunting," which is related to hello. Compare colloquial yeller for yellow, etc. Related: Hollered; hollering.

1896, from holler (v.); earlier hollar (1825). As a style of singing (originally Southern U.S.), attested by 1936.