cleave¹ / klēv/ • v. (past clove / klōv/ or cleft / kleft/ or cleaved / klēvd/ past part. clo·ven / ˈklōvən/ or cleft or cleaved) [tr.] split or sever (something), esp. along a natural line or grain: the large ax his father used to cleave wood for the fire. ∎  split (a molecule) by breaking a particular chemical bond. ∎  make a way through (something) forcefully, as if by splitting it apart: they watched a coot cleave the smooth water [intr.] an unstoppable warrior clove through their ranks. ∎  [intr.] Biol. (of a cell) divide.DERIVATIVES: cleav·a·ble adj.cleave² • v. [intr.] (cleave to) poetic/lit. stick fast to: Rose's mouth was dry, her tongue cleaving to the roof of her mouth. ∎  adhere strongly to (a particular pursuit or belief): part of why we cleave to sports is that excellence is so measurable. ∎  become very strongly involved with or emotionally attached to (someone): it was his choice to cleave to the Brownings.

cleave 2 stick fast, adhere. The present form repr. OE. cleofian, clifan = OS. cliƀon, OHG. klebēn (G. kleben) :- WGmc. wk. vb. *kliƀōjan, -ǣjan, f. *kliƀ-, the strong form of which is repr. by OE. clīfan = OS. biklīƀan (Du. beklijven), OHG. klīban, ON. klífa; f. Gmc. *klī́- stick, adhere (cf. CLAY, CLIMB). Cleft dates from XVII.

cleave 1 cut asunder, split. OE. clēofan str. vb. = OS. klioƀan, OHG. kliuban (G. klieben), ON. kljūfa :- Gmc. *kleuƀan, f. IE. base *gleubh- (cf. Gr. glūphein hollow out, L. glūbere peel).
Hence cleaver XVI.