The story
Since the 1880s, as explained in Wikipedia at ton of refrigeration § History.
Etymology from Wiktionary, CC BY-SA 4.0.
ton of refrigeration
Today it means: A unit of power chiefly applied to the cooling capacity of a refrigerator, freezer, or air conditioner, equal to 12,000 British thermal units (Btu) per hour (200 Btu per minute); it denotes the amount of heat required to melt one short ton of ice in 24 hours. Full definition →