The Collaborative International Dictionary
Col-
Col- \Col-\ A prefix signifying with, together. See Com-. [1913 Webster] ||
Douglas Harper's Etymology Dictionary
col-
form of Latin com- before stems beginning in -l- (see com-).
Wiktionary
col-
pre. 1 {{non-gloss definition|The form of (term con- English) used before ''l''.}} 2 {{non-gloss definition|A variant of (term colo- English) sometimes used before a vowel.}}