"long rope with a running noose," used for catching horses and cattle, 1808, earlier laço (1768), American English, from Spanish lazo "a snare, slipknot," from Latin laqueum (nominative laqueus) "noose, snare" (see lace (n.)). As a verb from 1807. Related: Lassoed; lassoing. A lasso can serve as a lariat, but the reverse is not true.
updated on May 18, 2016