I agree with you that they are rockets, but JATO is the term that was used back in the day and is the common term that the Blue Angels used to describe Fat Albert’s spectacular takeoff.
https://en.wikipedia.org/wiki/JATO: “JATO (acronym for jet-assisted take-off), is a type of assisted take-off for helping overloaded aircraft into the air by providing additional thrust in the form of small rockets. The term JATO is used interchangeably with the (more specific) term RATO, for rocket-assisted take-off (or, in RAF parlance, RATOG, for rocket-assisted take-off gear).”