Green’s Dictionary of Slang

(US campus) to throw away into a wastepaper bin.

1934		Weseen Dict. Amer. Sl. 333: [General] File – To throw in the wastebasket.
1944		P. Kendall Dict. Service Sl. n.p.: file it . . . make a straight toss to the wastebasket.
1980		G. Liddy Will 53: I wrote off the testing fee and filed the report.
1982		Eble Campus Sl. Fall 2: file – to throw away: File this can, please.