Should the stooper guess correctly, they all change places, and the jumper forms the back.
The boy who in jumping knocks off either of the things has to take the place of the stooper.
"bend forward," Old English stupian "to bow, bend" (cognate with Middle Dutch stupen "to bow, bend"), from Proto-Germanic *stup-, from PIE *(s)teu- (see steep (adj.)). Figurative sense of "condescend" is from 1570s. Sense of "swoop" is first recorded 1570s in falconry.
"raised open platform at the door of a house," 1755, American and Canadian, from Dutch stoep "flight of steps, doorstep, stoop," from Middle Dutch, from Proto-Germanic *stopo "step" (see step).
A person who looks on the ground at betting parlors and racetracks for betting tickets that may be valuable: The girl said she had become a stooper (1974+)