What is the X in X-mas?
late 14c., "process of understanding, reasoning, thought," from French discours, from Latin discursus "a running about," in Late Latin "conversation," from past participle stem of discurrere "run about," from dis- "apart" (see dis-) + currere "to run" (see current (adj.)). Sense of "formal speech or writing" is first recorded 1580s.
1540s, from discourse (n.). Related: Discoursed; discoursing.