1580s (transitive and intransitive), not found in Middle English, probably from a Low German source such as Middle Dutch splitten, from Proto-Germanic *spleitanan (source also of Danish and Frisian splitte, Old Frisian splita, German spleißen "to split"), from PIE *(s)plei- "to split, splice" (see flint).
U.S. slang meaning "leave, depart" first recorded 1954. Of couples, "to separate, to divorce" from 1942. To split the difference is suggested from 1715; to split (one's) ticket in the U.S. political sense is attested from 1842. To split hairs "make too-nice distinctions" is from 1670s (split a hair). Splitting image "exact likeness" is from 1880. To split the atom is from 1909.
1590s, "narrow cleft, crack, fissure," from split (v.). Meaning "piece of wood formed by splitting" is from 1610s. Meaning "an act of separation, a divorce" is from 1729. From 1861 as the name of the acrobatic feat. Meaning "a drink composed of two liquors" is from 1882; that of "sweet dish of sliced fruit with ice cream" is attested from 1920, American English. Slang meaning "share of the take" is from 1889. Meaning "a draw in a double-header" is from 1920.
1640s, past-participle adjective from split (v.). Split decision is from 1946 of court rulings, 1951 in boxing. Split shift is from 1904. Split personality first attested 1899.