What is the X in X-mas?
c.1600, "subjugated," past participle adjective from subdue. Meaning "calmed down, reduced in intensity" is recorded from 1822.
late 14c., "to conquer," from Old French souduire "deceive, seduce," from Latin subducere "draw, lead away, withdraw" (see subduce). The sense seems to have been taken in Anglo-French from Latin subdere. Subduct in the sense of "subtract" is from 1570s. Related: Subdued; subduing.