late 13c., conforten "to cheer up, console, soothe when in grief or trouble," from Old French conforter "to comfort, to solace; to help, strengthen," from Late Latin confortare "to strengthen much" (used in Vulgate), from assimilated form of Latin com-, here perhaps an intensive prefix (see com-), + fortis "strong" (see fort).
The change of -n- to -m- began in English 14c. In Middle English also "give or add strength to" (c. 1300); "encourage, urge, exhort" (c. 1300). Related: Comforted; comforting.
c. 1200, "feeling of relief in affliction or sorrow; solace, consolation" (as still in take comfort); also "source of alleviation or relief;" from Old French confort "consolation, solace; pleasure, enjoyment," from conforter "to solace; to help, strengthen" (see comfort (v.)). An Old English word in the same sense was frofor. Meaning "state of enjoyment resulting from satisfaction of bodily wants and freedom from anxiety" is from mid-13c. Also in Middle English "strength, support, encouragement" (late 14c.). Comforts (as opposed to necessities and luxuries) is from 1650s. Comfort food "food that provides a nostalgic or sentimental value but typically is of dubious nutritional value" is by 1987.