What is the X in X-mas?
early 15c., "to regain, take back;" mid-15c., "recommence, continue, begin again after interruption," from Middle French resumer (14c.) and directly from Latin resumere "take again, take up again, assume again," from re- "again" (see re-) + sumere "take up" (cf. assume). Meaning "begin again" is mid-15c. Intransitive sense "proceed after interruption" is from 1802. Related: Resumed; resuming.
also résumé, 1804, "a summary," from French résumé, noun use of past participle of Middle French resumer "to sum up," from Latin resumere (see resume (v.)). Meaning "biographical summary of a person's career" is 1940s.