Concise Bible Dictionary:

This was expressed by
1. yam, “the Sea,” referring to the Mediterranean, which lies on the west of Palestine (Gen. 12:8; and so forth).
2. maarab, δυσμή “sun-setting,” because the sun sets in the west (1 Chron. 7:28; Matt. 8:11).
3. maarabah, “sun-setting,” only in Isaiah 45:6.
4. mebo hashshemesh, from the “going down of the sun,” only in Joshua 23:4 and Zechariah 8:7.