|Detail from The Bayeux Tapestry (circa 1080).|
The dwarves cleaved to their king as the goblin horde closed from all sides.Words such as cleave are so common in English that there is a special name for them. Called auto-antonyms or contronyms, these words share a spelling with a word that has the opposite meaning. (We encountered another contronym when we considered the various meanings of bound.) Contronyms must give new English speakers fits.
The dwarf cleaved the goblin's helm with a mighty swing of his ax.
Cleave--meaning to adhere--comes from Middle English clevien, which derives from Old English clifian, which is akin to Old Saxon klibon, Old High German kliban, and Dutch kleven, all meaning to stick or cling.
Cleave--meaning to split--comes from Middle English cleven, which derives from Old English clēofan, which is akin to Old Saxon klioban, Old Norse kljūfa, Dutch kloven, and Old High German klioban, all meaning to split.
The two words have always been very similar, even across their ancestor languages, only a slight variation in spelling. It's easy to imagine how usage wore away the differences and left us with a confusing but interesting mess.