To cheat. The allusion is to filing money for the sake of the dust which can be used or sold. A file is a cheat. Hence “a jolly file,” etc.
“Sorful becom that fals file.”
Cursor Mundi MS.
“It was only on the faith of some grand expedition that the credulous rank and file of the Brotherhood subscribed their dollars.” —The Times ...
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894