tag (n.1)

"small, hanging piece from a garment," c. 1400, a word of uncertain origin. Middle English Compendium compares Middle Low German tagge "branch, twig, spike," also Norwegian tagg "point, prong, barb," Swedish tagg "prickle, thorn." Watkins has it from PIE *dek-, a root forming words referring to "fringe; horsetail; locks of hair" (see tail (n.1)). The sense development might be "point of metal at the end of a cord, string, etc.," hence "part hanging loose." Also compare tag (n.3).

The meaning "a label" (attached to a package, etc., with directions) is attested by 1835. The sense of "automobile license-plate" is recorded from 1935, originally U.S. underworld slang.

The meaning "an epithet, popular designation" is recorded from 1961, hence slang verb meaning "write graffiti in public places" (1990).

children's game in which one player ("it") chases the others and attempts to touch them, by 1738 (in a reference to "Queen Mary's reign"), perhaps a variation of Scottish tig "touch, tap" (1721, also attested as the name of the game), which is probably an alteration of Middle English tek, tik "touch, tap" (see tick (n.2)).

The baseball sense of "act of putting out an opposing player by touching him with the ball" is by 1912. It is not an acronym; it does not stand for anything.

early 15c. (implied in tagged), "furnish with a tag or tail," from tag (n.1). From 1620s as "mark by or as by a tag;" the sense of "fasten or join by or as if by a tag" is by 1704.

The meaning "go along as a follower" is from 1670s (verbal phrase tag along in this sense is by 1900). The colloquial transitive sense of "follow closely and persistently," as a dog its master, is by 1884. Related: Tagger; tagging.

"to hit lightly or touch in the game of tag," 1878, from tag (n.2) "a touch in the game of tag." The sense in baseball, "put out a player by touching him with the ball," is by 1904. Related: Tagged; tagger; tagging.

c. 1400, tagge "a point of metal or other hard thing at the end of a cord or chain, an aglet," a word of obscure origin, perhaps a variant of Middle English dagge, attested by late 14c as "ornamental incision in the edge of a garment;" by c. 1400 as "shred, tag, strip" (of cloth, leather). Middle English Compendium compares Old French dague "dagger" (see dagger (n.)).

Hence "any pendant thing or appendage;" and, collectively "the rabble" (1530s). with rag (n.); compare ragtag.