Probably from basis (through the notion of a foundation of power); a sovereign (abstractly, relatively, or figuratively) -- king.

see GREEK basis

βασιλέα (basilea) − 15 Occurrences

βασιλεῖ (basilei) − 6 Occurrences

βασιλεῖς (basileis) − 16 Occurrences

βασιλεῦ (basileu) − 9 Occurrences

βασιλεὺς (basileus) − 48 Occurrences

βασιλεῦσιν (basileusin) − 1 Occurrence

βασιλέων (basileōn) − 11 Occurrences

βασιλέως (basileōs) − 9 Occurrences