Old English heawan "to chop, hack, gash, strike with a cutting weapon or tool" (class VII strong verb; past tense heow, past participle heawen), earlier geheawan, from Proto-Germanic *hawwanan (source also of Old Norse hoggva, Old Frisian hawa, Old Saxon hauwan, Middle Dutch hauwen, Dutch houwen, Old High German houwan, German hauen "to cut, strike, hew"), from PIE *kau- "to hew, strike," a root more widely developed in Slavic (source also of Old Church Slavonic kovo, Lithuanian kauti "to strike, beat, fight;" Polish kuć "to forge," Russian kovat' "to strike, hammer, forge;" Latin cudere "to strike, beat;" Middle Irish cuad "beat, fight").
Weak past participle hewede appeared 14c., but hasn't yet entirely displaced hewn. Seemingly contradictory sense of "hold fast, stick to" (in phrase hew to), 1891, developed from earlier figurative phrase hew to the line "stick to a course," literally "cut evenly with an axe or saw." Related: Hewed; hewing.