Alexander is the Greek name “Αλέξανδρος”. It is a compound word (Αλέξ-ανδρος) consisting of two parts. The first part comes from the ancient verb “αλέξω” (“απωθώ” in modern Greek) which means repel, push away. The second part comes from the ancient noun “ανήρ” (“άνδρας” in modern Greek) which means man.
Actually “Αλέξανδρος” means the man who can repel, fight away other men. The one who is unbeatable, undefeated.