"It Must Be Jelly, "Cause Jam Don't Shake Like That" -Fats Waller, Glenn Miller & others.

in the US, JELLO is a trademarked dessert made with gelatin, Jelly is fruit spread made with gelatin, Jam is fruit spread made without gelatin.

(sung)"Oh, the big red letters stand for the Jello fam-i-ly-
The big red letters stand for the Jello fam-i-ly.."
(chanted)"Strawberry, Raspberry, Cherry, Orange, Lemon and Lime...My Daddy LIKES it!"
.....Fanny Bryce as "Baby Snooks" on the radio- ca. 1948

Jello was VERY common in my Kansas home...yes, often with the little marshmallows!