Green’s Dictionary of Slang

(US campus/UK juv.) an unpleasant, stupid person; can be used affectionately.

1983		Eble Campus Sl. Nov. 5: spag – term of address for a female friend: Hello, Nancy. Hi there, Spag.
2001		OnLine Dict. of Playground Sl. 🌐 spag, spagga n. variations on spacka.