consolate v.

word-forming element usually meaning "with, together," from Latin com, archaic form of classical Latin cum "together, together with, in combination," from PIE *kom- "beside, near, by, with" (compare Old English ge-, German ge-). The prefix in Latin sometimes was used as an intensive.

Before vowels and aspirates, it is reduced to co-; before -g-, it is assimilated to cog- or con-; before -l-, assimilated to col-; before -r-, assimilated to cor-; before -c-, -d-, -j-, -n-, -q-, -s-, -t-, and -v-, it is assimilated to con-, which was so frequent that it often was used as the normal form.

"comfort in grief; that which brings consolation," c. 1300, solas, from Old French solaz "pleasure, entertainment, enjoyment; solace, comfort," from Latin solacium "a soothing, assuaging; comfort, consolation," from solatus, past participle of solari "to console, soothe," from a suffixed form of PIE root *selh- "to reconcile" (source also of Greek hilaros).

Also 14c.-15c. sometimes solaunce, with substitution of -ance suffix. To make solace in Middle English was "enjoy oneself sexually," also "give (a horse) a rest." The adjectival form solacious "pleasantly agreeable, affording comfort" was "common c 1500-1650" [OED].

"alleviate the grief or mental distress of," 1690s, from French consoler "to comfort, console," from Latin consolari "offer solace, encourage, comfort, cheer," from assimilated form of com-, here perhaps an intensive prefix (see com-), + solari "to comfort" (see solace (n.)). Or perhaps a back-formation from consolation. The Latin word is glossed in Old English by frefran. Related: Consoled; consoling.