[portion of something belonging to an individual], Middle English share, from Old English scearu "a cutting, shearing, tonsure; a part or division, a piece cut off," from the source of sceran "to cut," from Proto-Germanic *skeraz (source also of Old High German scara "troop, share of forced labor," German Schar "troop, band," properly "a part of an army," Old Norse skör "rim"), from PIE root *sker- (1) "to cut," and compare share (n.2).
In Old English mostly in compounds: landscearu "a share of land," folcscearu "a division of the people." By late 14c. as "part or definite portion of a thing owned by a number in common" (in reference to booty or war prizes); the specific commercial meaning "part of the capital of a joint stock company" is attested by c. 1600.
The same Old English noun in the sense "division" led to an obsolete noun share "fork ('division') of the body at the groin; pubic region" (late Old English and Middle English); hence share-bone "pubis" (early 15c.).
"broad iron blade of a plow," Middle English share, from Old English scear, scær "plowshare," properly "that which cuts," from Proto-Germanic *skeraz (source also of Old Saxon sker "razor;" Old Frisian sker, schere, Middle Low German schar, Old High German scar "plowshare," also German Schar, Dutch ploegschaar, Middle High German pfluocschar), from PIE root *sker- (1) "to cut." Compare shear (v.).
1580s, "to apportion to someone as his share; to apportion out to others; to enjoy or suffer (something) with others," from share (n.1). The meaning "to divide one's own and give part to others" is recorded from 1590s; also "have a part, get one's portion;" also, of two or more, "to each take a portion."
The sense of "confess one's sins openly" (1932, implied in sharing) is said in OED to be from the Moral Rearmament movement, in which "the sharing of our sins and temptations with another Christian life given to God" was a principal spiritual activity. Share and share alike is attested from 1560s. Related: Shared; sharing.
"one who divides or apportions; one who shares with others," c. 1600, agent noun from share (v.).
"the part of a plow which cuts the ground at the bottom of the furrow and raises the slice to the mold-board to be turned," late 14c., from plow + share (n.2). To beat (one's) swords into plowshares as an image of peace made among peoples formerly at strife is from the Old Testament (Isaiah ii.4, Micah iv.3).
also *ker-, Proto-Indo-European root meaning "to cut."
It forms all or part of: bias; carnage; carnal; carnation; carnival; carnivorous; carrion; cenacle; charcuterie; charnel; corium; cortex; crone; cuirass; currier; curt; decorticate; excoriate; incarnadine; incarnate; incarnation; kirtle; scabbard; scar (n.2) "bare and broken rocky face of a cliff or mountain;" scaramouche; scarf (n.2) "connecting joint;" scarp; score; scrabble; scrap (n.1) "small piece;" scrape; screen; screw; scrimmage; scrofula; scrub (n.1) "low, stunted tree;" scurf; shard; share (n.1) "portion;" share (n.2) "iron blade of a plow;" sharp; shear; shears; sheer (adj.) "absolute, utter;" shirt; shore (n.) "land bordering a large body of water;" short; shrub; skerry; skirmish; skirt.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit krnati "hurts, wounds, kills," krntati "cuts;" Hittite karsh- "to cut off;" Greek keirein "to cut, shear;" Latin curtus "short," caro (genitive carnis) "flesh" (originally "piece of flesh"); Lithuanian skiriu, skirti "to separate;" Old English sceran, scieran "to cleave, hew, cut with a sharp instrument;" Old Irish scaraim "I separate;" Welsh ysgar "to separate," ysgyr "fragment."