The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
ker-1
DEFINITION:
Horn, head; with derivatives referring to horned animals, horn-shaped objects, and projecting parts. Oldest form *er-, becoming *ker- in centum languages. Derivatives include horn, unicorn, hornet, reindeer, migraine, cheer, rhinoceros, and cerebrum. I. Zero-grade form *k-.1. Suffixed form *k-no-.a. (i)horn, hornbeam, from Old English horn, horn; (ii)alpenhorn, althorn, flügelhorn, hornblende, from Old High German horn, horn. Both (i) and (ii) from Germanic *hurnaz. II. Extended o-grade form *koru-.1.corymb, from Greek korumbos, uppermost point (< head). 2.coryphaeus, from Greek koruph, head. 3. Suffixed form *koru-do-.corydalis, from Greek korudos, crested lark. 4. Suffixed form *koru-n-.corynebacterium, from Greek korun, club, mace. III. Extended e-grade form *keru-.1. Suffixed form *kerw-o-, having horns. a.cervine, serval, from Latin cervus, deer; b.cervix, from Latin cervx, neck. 2. Suffixed form *keru-do-.a.hart, from Old English heorot, hart, stag; b.hartebeest, from Middle Dutch hert, deer, hart. Both a and b from Germanic *herutaz. IV. Italic and Celtic blend of (I) *k-no- and (II) *koru- yielding *kor-nu-.corn2, cornea, corneous, corner, cornet, corniculate, cornu; bicornuate, Capricorn, cornification, lamellicorn, longicorn, tricorn, unicorn, from Latin corn, horn. V. Extended zero-grade form *k-.1.charivari; cheer, from Greek kar,kar, head. 2.carotid, from Greek karoun, to stupefy, be stupefied (< to feel heavy-headed). 3.carrot, carotene, from Greek karton, carrot (from its hornlike shape). VI. Suffixed further extended form *ks-no-.1.cranium; migraine, olecranon, from Greek krnion, skull, upper part of the head. 2.hornet, from Old English hyrnet, hornet, from Germanic *hurznuta-. VII. E-grade further extended form *kers-.1.carat, cerastes, kerato-; ceratodus, ceratopsian, chelicera, cladoceran, keratin, Monoceros, rhinoceros, triceratops, from Greek keras, horn. 2.sirdar, tarboosh, from Persian sar, head. 3. Suffixed form *kers-ro.cerebellum, cerebrum, saveloy, from Latin cerebrum, brain. VIII. Extended form *krei-.1.reindeer, from Old Norse hreinn, reindeer, from Germanic *hraina-.2.rinderpest, from Old High German hrind, ox, from Germanic *hrinda-.3. Possibly extended form *kr-.criosphinx, from Greek kros, ram. (Pokorny 1. er- 574.)