Klutz

Noun

 * 1) 🇺🇸 A clumsy or stupid person; an oaf.
 * 2) *"Mel, back home we'd call you a klutz." Melissa: "Use a lot of Yiddish back in Texas, do you?"
 * — Ultimate Daredevil and Elektra.
 * 1) *"Out of [one abortion doctor's] first six months of work, there are nine malpractice suits ... After it was apparent the guy was a klutz, they kept using him, and trying to cover for him, because they couldn't find another provider."
 * — Dr. Robert Crist, abortion doctor, St. Petersburg Times, June 3, 1990

Thesaurus
asshole, blockhead, blunderer, blunderhead, boob, booby, boor, botcher, bumbler, bungler, chump, clod, clodhopper, clodknocker, clot, clown, ding-a-ling, dingbat, dingdong, dolt, fumbler, galoot, gawk, goof, gowk, jerk, jerk-off, lobster, looby, lout, lubber, lug, lummox, lump, mutt, oaf, ox, palooka, prize sap, sap, saphead, sawney, schlemiel, slouch, slubberer, yokel

Etymology
The term is perhaps derived from the קלאָץ:, cognate with German Klotz:.