tab (n.1) Look up tab at Dictionary.com
"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) Look up tab at Dictionary.com
"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) Look up tab at Dictionary.com
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.) Look up tab at Dictionary.com
"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).