The origin of the expression must lie in the fact that the train of the robe lay loose on the ground around the person as he squatted—exactly the feature on which 1 Samuel 24 plays. The Essenes of Qumran appear to have used a similar expression. According to Josephus, they “covered themselves round with their garment,” so as not to “affront the Divine rays of light.” In this way they squatted over a small pit, dug with a paddle, in a lonely place. The point is, they literally covered their feet when defecating, taking this to be the logical extension of the interdict on exposing excrement to Yahweh. See The Life and Works of Flavius Josephus, tr. William Whiston (Chicago: John C. Winston, n.d.), where the reference is Jewish Wars 2.148–149.

See also column 46, lines 13–16 of the Temple Scroll (Yigael Yadin, The Temple Scroll, vol. 2 [Jerusalem: Israel Exploration Society, 1983], pp. 199–200). This is the well-known passage effectively prohibiting Essenes from attending to their bodily needs on the Sabbath. Incidentally, as Yadin read the text (and I concur), it calls for the construction of outhouses with “beaming” and “pits inside them”—that is, something like the construction of Eglon’s throne-room.