In "Professor" Jerry Thomas's _The Bon Vivant's Companion or How to Mix
Drinks_ there is a recipe for "Punch Jelly" (recipe #28), which consists of
making a punch and mixing it with gelatin and allowing it to set in molds. It
warns:
"This preparation is a very agreeable refreshment on a cold night, but should
be used in moderation; the strength of the punch is so artfully concealed by
its admixture with the gelatine, that many persons, particularly of the softer
sex, have been tempted to partake so plentifully of it as to render them
somewhat unfit for waltzing or quadrilling after supper."
So Jello Shots weren't a product of the 1990s, but of the 19th century!