Word Origin & History
cleave (1)
"to split," O.E. cleofan "to split, separate" (class II strong verb, past tense cleaf, past participle clofen), from P.Gmc. *kleubanan, from PIE base *gleubh- "to cut, slice." The old, strong p.t. clave was still alive at the time of the King James Bible; and the p.p. cloven survives, though mostly in compounds. Cleavage in geology is from 1816. The sense of "cleft between a woman's breasts in low-cut clothing" is first recorded 1946, when it was defined in a "Time" magazine article as the "Johnston Office trade term for the shadowed depression dividing an actress' bosom into two distinct sections" [Aug. 5].
[kleev] 
verb, cleft or cleaved or clove, cleft or cleaved or clo⋅ven, cleav⋅ing.