I have only been here for forty-five years and likewise unaware of “Little Saint Nick”. Not that I have never heard it, if I did it did not make an impression. Now I have spent about a total of five hours in malls during the “Holiday Season” in the last forty years, so that might affect my awareness.
“Little Saint Nick” was released by the Beach Boys in 1963 but didn’t chart. It only joined the Christmas playlists years later.