What is the X in X-mas?
Old English clæne "free from dirt or filth; pure, chaste, innocent; open, in the open," of beasts, "ritually safe to eat," from West Germanic *klainoz "clear, pure" (cf. Old Saxon kleni "dainty, delicate," Old Frisian klene "small," Old High German kleini "delicate, fine, small," German klein "small;" English preserves the original Germanic sense), from PIE root *gel- "bright, gleaming" (cf. Greek glene "eyeball," Old Irish gel "bright").
"Largely replaced by clear, pure in the higher senses" [Weekley], but as a verb (mid-15c.) it has largely usurped what once belonged to cleanse. Meaning "whole, entire" is from c.1300 (clean sweep in the figurative sense is from 1821). Sense of "innocent" is from c.1300; that of "not lewd" is from 1867; that of "not carrying anything forbidden" is from 1938; that of "free of drug addiction" is from 1950s. To come clean "confess" is from 1919, American English.
mid-15c., "make clean," from clean (adj.). Related: Cleaned; cleaning. From clean out "clean by emptying" comes sense of "to leave bare" (1844); cleaned-out "left penniless by losses" is from 1812.
Old English clæne "dirtlessly," also "clearly, fully, entirely;" see clean (adj.). Cf. similar use of German rein "clean."
To tell the truth, esp the whole truth; make a plenary confession (1919+)
: I was crazy about Lester. He played so clean and beautifulRelated Terms
The various forms of uncleanness according to the Mosaic law are enumerated in Lev. 11-15; Num. 19. The division of animals into clean and unclean was probably founded on the practice of sacrifice. It existed before the Flood (Gen. 7:2). The regulations regarding such animals are recorded in Lev. 11 and Deut. 14:1-21. The Hebrews were prohibited from using as food certain animal substances, such as (1) blood; (2) the fat covering the intestines, termed the caul; (3) the fat on the intestines, called the mesentery; (4) the fat of the kidneys; and (5) the fat tail of certain sheep (Ex. 29:13, 22; Lev. 3:4-9; 9:19; 17:10; 19:26). The chief design of these regulations seems to have been to establish a system of regimen which would distinguish the Jews from all other nations. Regarding the design and the abolition of these regulations the reader will find all the details in Lev. 20:24-26; Acts 10:9-16; 11:1-10; Heb. 9:9-14.