Etymology Back-formation from various words ending in “arian”, some directly derived from Classical or Medieval Latin words ending in -arius by adding -an to the stem, other indirectly via Old French words ending in "arien(ne)" or "erien(ne)" or from English words ending in “ary” to which -an was suffixed; note the same phenomenon in -ary. Equivalent to -ary + -an.
1
Morpheme A believer in something.
2
Morpheme An advocate of something.
3
Morpheme, Uncommon A native or inhabitant of somewhere.
-arian
suffix
Etymology By surface analysis, -ari(um) + -an and -ari(a) + -an.
1
Morpheme Used to form an adjective meaning "of or pertaining to" from nouns ending in -arium.
aquarium + -arian → aquarian (“of or pertaining to aquariums”)
planaria + -arian → planarian (“of or pertaining to planaria”)
1 more example
vitellarium + -arian → vitellarian (“of or pertaining to vitellaria”)