twerp
n.
of unknown origin; OED and Barnhart give earliest date as 1925, but the "Dictionary of American Slang" gives a first reference of 1874 (but without citation and I can't find it), which, if correct, would rule out the usual theory that it is from the proper name of T.W. Earp, a student at Oxford c.1911, who kindled wrath "in the hearts of the rugger-playing stalwarts at Oxford, when he was president of the Union, by being the last, most charming, and wittiest of the 'decadents.' " [Rawson]
"Mean to say you never heard of Sinzy? Why, he's one of the greatest characters in this town. He's a terrible twerp to look at -- got a face like bad news from home, but I guess he's the best jazz piano player in the world." [Julian Street, "Cross-Sections," 1923]