Green’s Dictionary of Slang

(US teen) a gob of phlegm or spit.

1969		Current Sl. III:4.
1974		Frank Zappa ‘Pygmy Twylyte’ 🎵 Green hocker croakin’ / In the Pygmy Twylyte.
1993		T. Jones Pugilist at Rest 49: Vittorio asked me if he could see my tonsils [...] and when I opened my mouth, he spat a hocker into the back of my throat.
2001		J. Stahl Plainclothes Naked (2002) 210: To cap the fun, the boy worked up a hock, grinned, and spit a goober the size of a chicken head onto Tony’s cheek.
2011		D.R. Pollock Devil All the Time 96: He had lain on the sticky floor among the cigarette butts and hockers and spilled beer.