<P> "File 13" is a euphemism for the trash can . The phrase is especially used in the U.S. military, and is less common outside of the United States . In the United Kingdom, for instance, the expression "round file" or "circular file" is more common (in reference to trash cans typically being round). Many Unix - like operating systems have a similar reference known as / dev / null . Expressions such as "I'll place that memo in file 13" are often heard in offices as a joking way of saying, "I'm going to throw away that memo ." </P> <P> The first known citation of "File 13" was in 1941 . The phrase's origins may perhaps be traced to 13 being a supposedly unlucky number, although the exact source is unknown . Another explanation refers to the fact that there are 12 months in the year, and a file is typically kept for each, with the 13th file being non-existent (the garbage can). An explanation given in the NZ military is based on the use of stencil lettering, where a capital B (as used for' bin') looks like a 13 . Or the possibility that trash cans were 13 inches by 13 inches in size . </P>

Where did the phrase file 13 come from