Old English ælc (n., pron., adj.) "any, all, every, each (one)," short for a-gelic "ever alike," from a "ever" (see aye (adv.)) + gelic "alike" (see like (adj.)). From a common West Germanic expression *aina-galīk (source also of Dutch elk, Old Frisian ellik, Old High German iogilih, German jeglich "each, every"). Originally used as we now use every (which is a compound of each) or all; modern use is by influence of Latin quisque. Modern spelling appeared late 1500s. Also see ilk, such, which.
"identical, equal; unchanging; one in substance or general character," from Proto-Germanic *samaz "same" (source also of Old Saxon, Old High German, Gothic sama, Old High German samant, German samt "together, with," Gothic samana "together," Dutch zamelen "to collect," German zusammen "together"), from PIE *samos "same," from suffixed form of root *sem- (1) "one; as one, together with."
Old English seems to have lost the adjective except in the adverbial phrase swa same "the same as" (literally "so same"). But the word that emerged in Middle English as "the ordinary adjectival pronominal designation of identity" [OED] is considered to be more likely (or mostly) from the Old Norse cognate same, samr "same." In its revival it replaced synonymous ilk.
As a pronoun, "the person or thing just mentioned," from c. 1300. In Middle English also a verb and an adjective, "together, mutually" (as in comen same "gather together, unite," kissen same "embrace one another").
Colloquial phrase same here "the same thing applies to me" as an exclamation of agreement is from 1895. All the same is from 1803 as "nevertheless, in spite of what has been mentioned." Same difference, a curious way to say "not different; equal," is attested from 1945. Often expanded for emphasis: ilk-same (mid-13c.); the self-same (early 15c.); one and the same is in Wyclif (late 14c.), translating Latin unus atque idem.
"a gathering of witches," 1660s, earlier "a meeting, gathering, assembly" (c. 1500); a variant form of covent, cuvent, from Old French covent, convent, from Latin conventus (see convent).
Covent (13c.) also meant "group of men or women in a monastery or convent." The variant form, and the association of this spelling of the word with witches, arose in Scotland but was not popularized until Sir Walter Scott used it in this sense in "Letters on Demonology and Witchcraft" (1830).
Efter that tym ther vold meit bot somtymes a Coven, somtymes mor, somtymes les; bot a Grand Meitting vold be about the end of ilk Quarter. Ther is threttein persones in ilk Coeven; and ilk on of vs has an Sprit to wait wpon ws, quhan ve pleas to call wpon him. I remember not all the Spritis names; bot thair is on called "Swein," quhilk waitis wpon the said Margret Wilson in Aulderne; he is still clothed in grass-grein .... ["Criminal Trials in Scotland," III, appendix, p.606, confession of Issobell Gowdie in Lochloy in 1662]