Enfilade (French) means literally to spin out; to put thread in [a needle], as enfiler une aiguille; to string beads by putting them on a thread, as enfiler des perles. Soldiers being compared to thread, we get the following metaphors: to go through a place as thread through a needle - to string artillery by placing it in
a line and directing it against an enemy; hence, to scour or rake with shot.

I think this explanation is a bit off. From Military Medicine I remember that enfilade means to have a
file of column of the enemy in a line, with our artillery in line with it, so that instead of "killing two birds
with one stone" it may be possible to kill hundreds of the enemy because aiming is so easy, and shots
both high and low will hit target.

I am reminded of old timer who boasted of shooting a couple dozen starlings that were on a telephone line
perfectly enfiladed so that just about every pellet of his shotgun shell hit a bird. Starlings were very much
hated in those days for driving away more desirable songbirds.