It could also be from the British Celtic word 'Maglorīx' with elements meaning 'prince' or 'king'. Maglorius being a Latinized form of this. Also related to 'Meylor' or 'Mailer' as a surname. And the Welsh 'Meilyr'.https://discover.23andme.com/last-name/Meylor
https://discover.23andme.com/last-name/Meylor