tab (n.1)

"small flap or strip of material," c. 1600, possibly from a dialectal word, of uncertain origin. Often interchangeable with tag (n.1). Compare also Middle English tab "strap or string" (mid-15c.), Norwegian dialectal tave "piece of cloth, rag."

tab (n.2)

"account, bill, check," 1888, American English colloquial, probably a shortened form of tabulation or of tablet in the sense "a sheet for writing on." Figurative phrase keep a tab on is recorded from 1890.

tab (n.3)

1961, shortened form of tablet (especially one of sugar containing LSD). As an abbreviation of tabloid (newspaper) it is 1990s slang. As a short form of tabulator key of a typewriter (later computer) it is recorded from 1916.

tab (v.)

"designate, label, name," 1924, earlier "affix a tab to" 1872 (implied in tabbed), perhaps an alteration of tag (v.2). Related: Tabbing. Also see tab (n.1).