"to loll idly," c.1500, Scottish, of uncertain origin, perhaps [Barnhart] from French s'allonger (paresseusement) "to lounge about, lie at full length," from Old French alongier "lengthen," from Latin longus "long" (see long (adj.)). Another etymology traces it through obsolete lungis (n.) "slow, lazy person" (c.1560), from Middle French longis, a generic application of Longinus, supposed to be the name of the centurion who pierced Christ's side with a spear in John xix:34. Popular etymology associated the name directly with long (adj.). Related: Lounged; lounging.
"comfortable drawing room," 1881, from lounge (v.); in the sense of "couch on which one can lie at full length," it is attested from 1830. Lounge lizard is by 1917, perhaps from 1912, a term of contempt, originally in reference to men who hung around in tea rooms to flirt.