What is the X in X-mas?
Old English hydan "to hide, conceal; preserve; hide oneself; bury a corpse," from West Germanic *hudjan (cf. Middle Dutch, Middle Low German huden), from PIE *keudh- (cf. Greek keuthein "to hide, conceal"), from root *(s)keu- "to cover, conceal" (see hide (n.1)). Hide and seek (by 1670s), children's game, replaced earlier all hid (1580s).
"skin of a large animal," Old English hyd "hide, skin," from Proto-Germanic *hudiz (cf. Old Norse huð, Old Frisian hed, Middle Dutch huut, Dutch huid, Old High German hut, German Haut "skin"), related to Old English verb hydan "to hide," the common notion being of "covering."
All of this is from PIE root *(s)keu- "to cover, conceal" (cf. Sanskrit kostha "enclosing wall," skunati "covers;" Armenian ciw "roof;" Latin cutis "skin," scutum "shield," ob-scurus "dark;" Greek kytos "a hollow, vessel," keutho "to cover, to hide," skynia "eyebrows;" Russian kishka "gut," literally "sheath;" Lithuanian kiautas "husk," kutis "stall;" Old Norse sky "cloud;" Old English sceo "cloud;" Middle High German hode "scrotum;" Old High German scura, German Scheuer "barn;" Welsh cuddio "to hide").
The alliterative pairing of hide and hair (often negative, hide nor hair) was in Middle English (early 15c.), but earlier and more common was hide ne hewe, literally "skin and complexion ('hue')" (c.1200).
"measure of land" (obsolete), Old English hid "hide of land," earlier higid, from hiw- "family" (cf. hiwan "household," hiwo "a husband, master of a household"), from Proto-Germanic *hiwido-, from PIE *keiwo- (cf. Latin civis "citizen"), from root *kei- "to lie; bed, couch; beloved, dear" (see cemetery, and cf. city).
The notion was of "amount of land needed to feed one free family and dependents," usually 100 or 120 acres, but the amount could be as little as 60, depending on the quality of the land. Often also defined as "as much land as could be tilled by one plow in a year." Translated in Latin as familia.
the pelt taken from a cow, steer, or bull of the bovine species, from the pelt of a horse, or from the integument of some other large adult animal. The pelts of smaller animals are commonly called skins-namely, sheepskins, goatskins, calfskins, etc. For the preservation and tanning of hides, see leather.