The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
bhel-2
DEFINITION:
To blow, swell; with derivatives referring to various round objects and to the notion of tumescent masculinity. Derivatives include boulevard, boulder, phallus, balloon, ballot, and fool. 1. Zero-grade form bh-.a.bowl1, from Old English bolla, pot, bowl; b. bole, from Old Norse bolr, tree trunk; c.bulk, from Old Norse bulki, cargo (< rolled-up load); d.rocambole, from Old High German bolla, ball; e.boulevard, bulwark, from Middle High German bole, beam, plank; f.boll, from Middle Dutch bolle, round object; g.biltong, from Middle Dutch bille, buttock; h.boulder, from a Scandinavian source akin to Swedish bullersten, rounded stone, boulder, from *buller-, round object. ah all from Germanic *bul-.2. Suffixed zero-grade form *bh-n-.a.bull1, from Old Norse boli, bull, from Germanic *bulln-;b.bullock, from Old English bulluc, bull, from Germanic *bulluka-;c.phallus; ithyphallic, from Greek phallos, phallus; d. possibly Latin full, a fuller: full2. 3. O-grade form *bhol-.a.bollix, from Old English beallucas, testicles; b.ball1, from Old English *beall, ball; c.bilberry, probably from a Scandinavian source akin to Danish bolle, round roll; d.balloon, ballot, ballottement, from Italian dialectal balla, ball; e.pall-mall, from Italian palla, ball; f.bale1, from Old French bale, rolled-up bundle. af all from Germanic *ball-.4. Possibly suffixed o-grade form *bhol-to-.a.bold, from Old English bald,beald, bold; b.bawd, from Old Saxon bald, bold; c.Balder, from Old Norse ballr, baldr, brave. ac from Germanic *balthaz, bold. 5. Suffixed o-grade form *bhol-n-.fils2, follicle, folly, fool, from Latin follis, bellows, inflated ball. 6. Possibly Greek phal(l)aina, whale: baleen. 7. Conceivably from this root (but more likely unrelated) is Greek phellos, cork, cork oak: phellem; phelloderm, phellogen. (Pokorny 3. bhel- 120.) The following derivatives of this root are entered separately: bhel-3, bhelgh-, bhleu-.