D&D comes from chain mail, a heroic fantasy miniature battle game inspired by naval miniature battle game. Hence the concept of character class (instead of boat class) and armour class (where the lower the better). But based on that, slowly the idea of playing a single character appeared and it turned into D&D and then early RPG

Modern RPG got (Somehow) rid of character class (even though some archetype/Playbooks are classes witha different name) and armour place. But D&D kept it by traditipn