What does Alexandros mean?
Greek Alexandros, from 'alexo' ('to defend, help') and 'aner/andros' ('man'), i.e. 'defender of men/people'. Borne by Alexander the Great.
What does Sirius mean?
The proper name of the brightest star in the night sky, from Greek 'Seirios' meaning 'scorching' or 'glowing'. Unlike most star names it is Greek rather than Arabic, and the literal sense is 'scorching/glowing' rather than 'star'.