rant v.

c. 1600, "to be jovial and boisterous," also "to talk bombastically," from Dutch randten (earlier ranten) "talk foolishly, rave," of unknown origin (compare German rantzen "to frolic, spring about," dialectal rant "noise, uproar"). Related: Ranted; ranting. Ranters as the name of an antinomian sect which arose in England c. 1645 is attested from 1651; applied 1823 to Primitive Methodists. A 1700 slang dictionary has rantipole "a rude wild Boy or Girl" (also as a verb and adjective); to ride rantipole meant "The woman uppermost in the amorous congress" [Grose].

"bombastic speech; boisterous, empty declamation; fierce or high-sounding language without much meaning or dignity of thought," 1640s, from rant (v.). In Scottish and northern England dialect it could mean "a boisterous, noisy frolic" (1670s).

Rant is extravagant or violent language, proceeding from or fanaticism, generally in support of extreme opinions against those holding opinions of a milder or different sort. [Century Dictionary, 1889]