|Easton's Bible Dictionary|
(correctly Shi'hor) black; dark the name given to the river Nile in Isaiah 23:3; Jeremiah 2:18. In Joshua 13:3 it is probably "the river of Egypt", i.e., the Wady el-Arish (1 Chronicles 13:5), which flows "before Egypt", i.e., in a north-easterly direction from Egypt, and enters the sea about 50 miles south-west of Gaza.
Int. Standard Bible Encyclopedia
Sihor (3 Occurrences)
Joshua 13:3 From Sihor, which is before Egypt, even unto the borders of Ekron northward, which is counted to the Canaanite: five lords of the Philistines; the Gazathites, and the Ashdothites, the Eshkalonites, the Gittites, and the Ekronites; also the Avites: (KJV WBS YLT)
Isaiah 23:3 And by great waters the seed of Sihor, the harvest of the river, is her revenue; and she is a mart of nations. (KJV WBS YLT)
Jeremiah 2:18 And now what hast thou to do in the way of Egypt, to drink the waters of Sihor? or what hast thou to do in the way of Assyria, to drink the waters of the river? (KJV WBS YLT)