What is the X in X-mas?
"to walk with regular tread," early 15c., from Middle French marcher "to march, walk," from Old French marchier "to stride, march," originally "to trample, tread underfoot," perhaps from Frankish *markon or some other Germanic source related to obsolete Middle English march (n.) "borderland" (see march (n.2)). Or possibly from Gallo-Roman *marcare, from Latin marcus "hammer," via notion of "tramping the feet." Meaning "to cause to march" is from 1590s. Related: Marched; marching. Marching band is attested from 1852. Italian marciare, Spanish marchar are said to be from French.
"act of marching," 1580s, from march (v.) or else from Middle French marche (n.), from marcher (v.). The musical sense first attested 1570s, from notion of "rhythmic drumbeat" for marching. Transferred sense of "forward motion" is from 1620s.
"boundary," late 13c. (in reference to the borderlands beside Wales, rendering Old English Mercia), from Old French marche "boundary, frontier," from Frankish *marka or some other Germanic source (cf. Old High German marchon "to mark out, delimit," German Mark "boundary;" see mark (n.1)). Now obsolete. There was a verb in Middle English (c.1300), "tohave a common boundary," from Old French marchier "border upon, lie alongside."
third month, c.1200, from Anglo-French marche, Old French marz, from Latin Martius (mensis) "(month) of Mars," from Mars (genitive Martis). Replaced Old English hreðmonaþ, the first part of which is of uncertain meaning, perhaps from hræd "quick, nimble, ready, active, alert, prompt." For March hare, proverbial type of madness, see mad.
third month of the Gregorian calendar. It was named after Mars, the Roman god of war. Originally, March was the first month of the Roman calendar.