Why is the ninth month called September?
1706, from French enfilade, from Old French enfiler (13c.) "to thread (a needle) on a string, pierce from end to end," from en- "put on" (see en- (1)) + fil "thread" (see file (v.)).
Used of rows of apartments and lines of trees before modern military sense came to predominate. As a verb from 1706. Related: Enfiladed; enfilading.