@aaaaa  I’m not sure are you trolling or not, but “mater” is not catholic influence.

As I said, it’s just the accusative form of the word “mati”. Which conjugation goes like this:
Nominative: mati
Genitive: matere
Dative: materi
Accusative: mater
Vocative: mati
Instrumental: materom
Locative: materi


South Slavic
Serbo-Croatian: mati
Old Bulgarian (as @NikeBG said): mati (“majka” in Modern Bulgarian)
Slovene: mati

East Slavic
Russian: мати (archaic), мать (modern)
Ukrainian: мати
Belorussian: мац

West Slavic
Czech: mati (archaic), matka (modern)
Slovak: mati (archaic), mať (modern)
Polish: mati (Old Polish), mać (Middle Polish), matka (Modern Polish)