The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
gwer-1
DEFINITION:
Heavy. Oldest form *gwer2-. Derivatives include grave2, grief, aggravate, baritone, guru, brute, and blitzkrieg. I. Zero-grade form *gw-.1. Suffixed form *gw-wi-.grave2, gravid, gravimeter, gravitate, gravity, grief, grieve; aggravate, aggrieve, from Latin gravis, heavy, weighty. 2. Suffixed form *gw-u-.a.barite, barium, baryon, baryta; baritone, barycenter, barysphere, charivari, from Greek barus, heavy; b.guru, from Sanskrit guru-, heavy, venerable. 3. Suffixed form *gw-es-.bar2, baro-; centrobaric, isallobar, isobar, from Greek baros, weight. 4. Possibly *gwr- in Greek compound *u(d)-bri- (see ud-). II. Suffixed extended form *gwr-to-.brut, brute, from Latin brtus, heavy, unwieldy, dull, stupid, brutish. III. Suffixed extended form *gwr-g-.a.brio, from Spanish brio or Provençal briu, vigor, from Celtic *brg-o-, strength; b.brig, brigade, brigand, brigantine, from Old Italian briga, strife, from Celtic *brg--, strife; c.blitzkrieg, sitzkrieg, from Old High German krg,chrg, stubbornness, from Germanic *krg-. IV. Suffixed full-grade form *gwer-n-, millstone. quern, from Old English cweorn, quern. (Pokorny 2. ger- 476.)