the.com/jack in the box

means A toy consisting of a box with a crank that plays a tune, culminating in a puppet — usually a clown or jester — springing out of the lid.

from The toy dates to at least the 18th century, but the name 'Jack-in-the-box' is older still, going back to a phrase for a trickster or impostor — 'Jack' being the generic everyman name used for rogues, sailors, and nobodies alike (as in jack-of-all-trades, jack-tar, cheapjack). There's also a medieval sense of 'Jack-in-the-box' meaning a swindler who tricked merchants with empty boxes passed off as valuable goods. Whether the toy borrowed its name from that con-artist sense, or simply described itself plainly — a jack (a sly little fellow) hidden in a box — isn't settled. Either way, the toy's genius is the same trick in miniature: you know exactly what's coming, and it gets you anyway.