mid-15c., of persons; 1540s, of actions or objects, "likely to bring luck;" from luck (n.) + -y (2). Meaning "occurring by chance" is 1590s. Related: Luckier; luckiest; luckiness.
Lucky break is attested from 1884 in billiards; 1872 as "failure or break-down which turns out to be fortunate." Lucky accident is from 1660s. Lucky dog "unusually lucky person" is from 1842. Lucky Strike as the name of a U.S. brand of cigarettes (originally chewing tobacco) popular in the World War II years is said to date from 1871. Its popularity grew from 1935 when the brand's maker picked up sponsorship of radio's "Your Hit Parade."