"Abecedarius" (or "abecedarium") is a Medieval Latin word meaning "ABC primer", derived by adding the suffix "-arius" (-a, -um) to the names of the first four letters of the alphabet (a+b+c+d).
The term "Abecedarius" signifies an ABC primer, which was likely used as an instructional tool in Medieval Latin, combining the names of the first four letters of the alphabet with a suffix that denotes a specific type of text.