The American Heritage® Dictionary of the English Language: Fourth Edition. 2000.
Appendix I
Indo-European Roots
ENTRY:
gel-
DEFINITION:
Cold; to freeze. Derivatives include chill, jelly, and glacier. 1.chill, from Old English c(i)ele, chill, from Germanic *kaliz, coldness. 2.cold, from Old English ceald, cold, from Germanic *kaldaz, cold. 3a.cool, from Old English cl, cold, cool; b.keel3, from Old English clan, to cool, from Germanic *kljan, to cool. Both a and b from Germanic *kl-, cool. 4. Suffixed form *gel--.gelatin, gelation, jelly; congeal, from Latin gelre, to freeze. 5. Suffixed form *gel-u-.gelid, from Latin gel, frost, cold. 6. Probably suffixed zero-grade form *g-k-.glacé, glacial, glaciate, glacier, glacis; verglas, from Latin glacis, ice. (Pokorny 3. gel()- 365.)
l, cold, cool; b. keel3, from Old English c
lan, to cool, from Germanic *k
-. gelatin, gelation, jelly; congeal, from Latin gel
, frost, cold. 6. Probably suffixed zero-grade form *g
-k-. glacé, glacial, glaciate, glacier, glacis; verglas, from Latin glaci
)- 365.) 
