Why Seraphim Have Six Wings

While this question seems to be along the lines of "How many angels can fit on the head of a pin". I found the answer, or rather the search for the answer, to be really fascinating.

First, to back up a hitch to why I came to care at all: my kids asked me.

I was listening to the Daily Readings on podcast as a way to get a little scripture in while I rushed around getting ready for work (grumble grumble). Saturday's OT reading was from Isaiah 6:1-7 in which Isaiah has the vision of the Lord attended by the Seraphim, the burning ones.

I saw the Lord seated on a high and lofty throne,
with the train of his garment filling the temple.
Seraphim were stationed above; each of them had six wings:
with two they veiled their faces,
with two they veiled their feet,
and with two they hovered aloft.

My kids were listening along with me and wanted to know why they had six wings instead of only two. Two for flying, that was easy; two to cover their faces for humility in the presence of God, okay; but the two to cover their feet just stumped me.

At first I thought of Moses at the Burning Bush who was told to take off his shoes because "the place where you are standing is holy ground". But that involves uncovering the feet, not covering them.

I found several references to covering the feet for modesty's sake as being less "honorable" than other parts, but that doesn't quite tell the tale. The consensus seems to be that the feet are sometimes euphemisms for genitalia in the OT. [Raises eyebrows].

This explanation from JEK:

Seraphim are mentioned in the Bible in Isaiah's vision of the heavenly throne-room (Is 6:1-7), where the LORD is seated between two seraphim. (In Hebrew, most masculine nouns form the plural by adding "-im".) Each has six wings, and with two he covers his face, and with two he covers his feet, and with two he flies. Later writers identify these functions with poverty, chastity, and obedience. Poverty, in that he veils his face, a sign of humility. Chastity, in that he covers his feet, a standard Hebrew idiom (or euphemism) for the lower body, including the crotch. Obedience, in that he flies to carry out whatever commission he receives from God.

Pretty interesting stuff. Now in all my brief (aka lazy) search for the answer I never did find a good solid Catholic exegetical source that was easily searchable. Anyone got any suggestions on where to find good Catholic sources?