"to place (papers) in consecutive order for future reference," late 15c., from M.Fr. filer "string documents on a wire for preservation or reference," from fil "thread, string," from L. filum "thread," from PIE base *gwhis-lom (cf. Armenian jil "sinew, string, line," Lith. gysla "vein, sinew," O.C.S. zila "vein"). The notion is of documents hung up on a line like drying laundry. Methods have become more sophisticated, but the word has stuck. The noun first attested in Eng. in the military sense, "line or row of men," 1590s, from M.Fr. filer in the sense of "spin out (thread), march in file." Related: Filed; filing. The noun meaning "arranged collection of papers" is from 1620s; computer sense is from 1954.
"metal tool," O.E. feol (Mercian fil), from P.Gmc. *finkhlo (cf. O.H.G. fila, M.Du. vile, Ger. Feile), probably from PIE *pik-/*peik- "cut" (cf. Skt. pimsati "hews out, carves," L. pingere "to paint," O.C.S. pila "file, saw," Lith. pela "file;" see paint). The verb in this sense is from early 13c. Related: Filed; filing.
[first sense perhaps fr the tool; perhaps related to French filou, ''pickpocket'']
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with on file
In or as if in a record for easy reference. For example, There's no job open right now, but we'll keep your résumé on file. The use of file in the sense of “a collection of papers stored for ready reference” dates from the early 1600s.