Shur

an enclosure; a wall, a part, probably, of the Arabian desert, on the north-eastern border of Egypt, giving its name to a wilderness extending from Egypt toward Philistia (Gen 16:7 ; 20:1; 25:18; Ex 15:22 ). The name was probably given to it from the wall (or shur) which the Egyptians built to defend their frontier on the north-east from the desert tribes. This wall or line of fortifications extended from Pelusium to Heliopolis.

EBD - Easton's Bible Dictionary