Query: "file 13" (throw sth. away)

[Sam Clements]

There's a 1945 cite in the NY Times from a GI, saying

"1.  War.
"(A) Lay off it, put it in File 13.

Together with a 1955 cite saying that File 13 is Pentagonese, and "deep six"
is Navy for the same thing, one concludes a military origin.

SC