Who the heck thought of mixing butter and rum and then heating it?

"Hot buttered rum, also known as a hot toddy, has a long history in the U.S. In fact, it predates the republic. The drink has its origins in Europe, where hot, spiced alcohol-spiked beverages have for centuries been used to fortify souls against bitterly cold winters. When the British Royal Navy captured Jamaica in 1655, rum replaced brandy as the sailors’ daily ration.

Colonists began importing it and soon moved on to setting up distilleries in the Northeast so they could make their own from cheap imported molasses. The liquor worked its way into traditional drinks such as the toddy, made with sugar or honey, boiling water and spices, and, in the case of hot buttered rum, enriched with a pat of butter."

American Food Roots: Hot Toddy