What is the X in X-mas?
late 14c., "observation as the source of knowledge; actual observation; an event which has affected one," from Old French esperience (13c.) "experiment, proof, experience," from Latin experientia "knowledge gained by repeated trials," from experientem (nominative experiens), present participle of experiri "to try, test," from ex- "out of" (see ex-) + peritus "experienced, tested," from PIE root *per- "to lead, pass over" (see peril). Meaning "state of having done something and gotten handy at it" is from late 15c.
1530s, "to test, try;" see experience (n.). Sense of "feel, undergo" first recorded 1580s. Related: Experiences; experiencing.
experience ex·pe·ri·ence (ĭk-spēr'ē-əns)
The feeling of emotions and sensations as opposed to thinking; involvement in what is happening rather than abstract reflection on an event.