From magis, more or great, + suffix -ter.
{{la-noun|magister|magistri|magistrī|m|second}}
{{la-decl-2nd-ER|magister|magister|magistr}}
de:magister et:magister fr:magister ko:magister io:magister lt:magister pl:magister pt:magister ru:magister fi:magister vi:magister