Upvote:7
I don't think they were collecting foreskins, and I believe this mistaken assumption is due to a mistranslation.
This goes back to the meaning of the word "ערלה" ("Orla") in Hebrew also meaning specifically foreskin, but also "uncut", or "un-refined". This isn't a new interpretation, this is just knowing the source language, as a brief survey of the use of the root of the word "ערל" ("Arel") in the bible confirms:
Thus, it is more likely that the story describes collection of genitals in the Egyptian custom, with the biblical author terming them "Orlot" or "the uncut(s)", which they were, and is not describing collection of the actual foreskin alone.
Upvote:15
The practice of Circumcision was by no means unknown in ancient Egypt, although I'm not sure how widely it was used.
A parallel to the Israelite practice of collecting the foreskins of slain enemies was the ancient Egyptian practice of collecting hands and/or genitals from the dead. Soldiers were rewarded for each "trophy" they brought back. The practice is recorded in a number of tombs, for example in the Biography of Ahmose, son of Abana.
The Israelites were probably collecting foreskins for the same reason (e.g. 1 Samuel 18:27). An additional benefit of counting the foreskins would be that, since the Israelite army was presumably already circumcised before the battle, they could be sure that any foreskins collected actually belonged to the enemy.