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"). Related: Ranted; ranting. Ranters "antinomian sect which arose in England c. 1645" is attested from 1651; applied 1823 to early 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].

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]

"boisterous, empty declamation; fierce or high-sounding language without much meaning or dignity of thought; bombast; a ranting speech," 1640s, from rant (v.).