Celsius got its name from Anders Celsius, a Swedish astronomer who developed the Celsius scale in 1742.

Originally, Celsius's scale had 0°C as the boiling point of water and 100°C as the freezing point, which is the opposite of how we use it today. It was later reversed by botanist Carl Linnaeus and others to make the scale more practical for everyday use.

Despite the reversal, the scale still bears Celsius's name in recognition of his initial work in developing it.