Probably from leibo (to pour a "libation"); the south(- west) wind (as bringing rain, i.e. (by extension) the south quarter) -- southwest.
1. the southwest wind: Herodotus 2, 25; Polybius 10, 10, 3; others.
2. the quarter of the heavens whence the southwest wind blows: Acts 27:12 (on which see βλέπω, 3 and κατά, II. 1 c.) (Genesis 13:14; Genesis 20:1; Numbers 2:10; Deuteronomy 33:23).