What is the X in X-mas?
early 14c., "outer garment," from Old French cote "coat, robe, tunic, overgarment," from Frankish *kotta "coarse cloth" or some other Germanic source (cf. Old Saxon kot "woolen mantle," Old High German chozza "cloak of coarse wool," German Kotze "a coarse coat"), of unknown origin. Transferred to animal's natural covering late 14c. Extended 1660s to a layer of any substance covering any surface. Spanish, Portuguese cota, Italian cotta are Germanic loan-words.
The outer covering or enveloping layer or layers of an organ or part.
the tunic worn like the shirt next the skin (Lev. 16:4; Cant. 5:3; 2 Sam. 15:32; Ex. 28:4; 29:5). The "coats of skins" prepared by God for Adam and Eve were probably nothing more than aprons (Gen. 3:21). This tunic was sometimes woven entire without a seam (John 19:23); it was also sometimes of "many colours" (Gen. 37:3; R.V. marg., "a long garment with sleeves"). The "fisher's coat" of John 21:7 was obviously an outer garment or cloak, as was also the "coat" made by Hannah for Samuel (1 Sam. 2:19). (See DRESS.)