From Middle English tocleven, from Old English tōclēofan (“to cleave apart, cleave in two”), equivalent to to- + cleve (“to cleave”). Cognate with English tocleave. More at to-, cleave.
to-cleve (third-person singular present to-cleves, present participle to-clevin, past to-claif, past participle to-claif)
- To split asunder.