boil
v.
early 13c., from Old French bolir "boil, bubble up, ferment, gush" (12c., Modern French bouillir), from Latin bullire "to bubble, seethe," from PIE base *beu- "to swell" (see bull, n.2). The native word is seethe. Figurative sense of "to agitate the feelings" is from 1640s.
I am impatient, and my blood boyls high. [Thomas Otway, "Alcibiades," 1675]
Related: Boiled; boiling. Boiling point is recorded from 1773.n.
"hard tumor," altered from Middle English bile (Kentish bele), perhaps by association with the verb; from Old English byl, byle "boil, carbuncle," from West Germanic *buljon- "swelling" (cognates: Old Frisian bele, Old High German bulia, German Beule). Perhaps ultimately from PIE root *bhel- (2) "to swell" (see bole), or from *beu- "to grow, swell" (see bull, n.2; also compare boast, n.). Compare Old Irish bolach "pustule," Gothic ufbauljan "to puff up," Icelandic beyla "hump."