This name is not Greek! It's pure Macedonian! It means "king" in Greek and nothing more. No explanation! Stolen word! (V-a-s-IL)=(In god from holy)=(Your Highness) IL = HOLY! The god of the Macedonians. This name and it's syllables are all in Macedonian language (not Greek!). About IL and Alexander the Great: We celebrate ILINDEN (IL's day)(the holy day) on 2nd of August (20th July by Julian calendar) It is the birthday of Alexander the Great (the Macedon) https://en.wikipedia.org/wiki/Republic_Day_(North_Macedonia) Some parts of Macedonia are still invaded by Greece (south) and Bulgaria (east) The invaded Macedonians still use their native names, but with adjectives like -is in Greece.
For some reason, this is often regarded as equivalent to William, an unrelated name that has no true equivalent in Greek. (It "should" be Basil, of course.)
https://el.wiktionary.org/wiki/%CE%92%CE%B1%CF%83%CE%AF%CE%BB%CE%B7%CF%82