Albert Barnes Commentary Deuteronomy 3:9

"([which] Hermon the Sidonians call Sirion, and the Amorites call it Senir;)" — Deuteronomy 3:9 (ASV)

Hermon, the southern and highest point of the Lebanon mountain range, was also the religious center of primeval Syria. Its Baal sanctuaries not only existed but also gave it a name before the Exodus.

Therefore, its various names were carefully specified. Its Sidonian name, for example, could easily have become known to Moses through the constant interaction that had occurred from the most ancient times between Sidon and Egypt.