Old English feortan, ultimately from PIE *perd- (source also of Old High German ferzan, Old Norse freta, Danish fjerte, Sanskrit pard, Greek perdein, Lithuanian perdžiu, persti, Russian perdet), of imitative origin. Related: Farted; farting. As a noun, from late 14c.
But "flatulence" is from a Latin root:
flatulent (adj.) "affected by digestive gas," 1590s, from Middle French flatulent (16c.), from Modern Latin flatulentus, from Latin flatus "a blowing, breathing, snorting; a breaking wind," past participle of flare "to blow, puff," from PIE root *bhle- "to blow."
English has Germanic fart and a French-Latin fart!
2 ways of farting! How gross.