*gwhi-

"narrow passage in a mountain region," 1640s, especially in a military sense, "a narrow passage down which troops can march only in single file," from French défilé, noun use of past participle of défiler "march by files" (17c.), from de- "off" (see de-) + file "row," from Latin filum "thread" (from PIE root *gwhi- "thread, tendon"). The verb, "to march off in a line or file," is by 1705, from French défiler.

1706, a string of things in a straight line, 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.1)). Used of rows of apartments and lines of trees before military sense came to predominate: "a firing with a straight passage down ranks of men, channels in fortifications, etc." (1796). As a verb from 1706 in the military sense, "rake with shot through the full length." Related: Enfiladed; enfilading. The Old French verb was borrowed in Middle English as enfile "to put (something) on a thread or string."