mid-15c., "a discourse," from Latin colloquium "conference, conversation," literally "a speaking together," from assimilated form of com "together" (see com-) + -loquium "speaking," from loqui "to speak" (from PIE root *tolkw- "to speak"). Meaning "conversation" is attested in English from 1580s.
colloquia
colloquial
colloquialism
colloquialize
colloquium
colloquy
collude
collusion
collusive
collywobbles
cologne