Green’s Dictionary of Slang

(US campus) an unpleasant, esp. boring, person.

1932		(con. 1910s) J.T. Farrell Young Lonigan in Studs Lonigan (1936) 88: He was afraid that he might be acting like a droop.
1940		Topeka Journal 23 Apr. 10: Don’t be a droop.
1950		Oh Boy! No. 13 8: Welcome back to the King of the Clots, Drip of the Droops – Stuporman!
1960, 1975		Wentworth & Flexner DAS.