Swedish astronomer Anders Celsius invented this measuring system in the year 1742. He originally put the freezing point at 100 and the boiling point at 0. Other scientists soon flipped the numbers into the logical modern form we use today.
For many years, people called it the centigrade scale instead of the Celsius scale. The prefix centi means hundred, and the word grade means steps. This name perfectly described the one hundred exact divisions between freezing and boiling.
In 1948, a global committee officially changed the name to honor Anders Celsius. They also wanted to avoid confusion with a geometry angle unit called a centigrade. Today, the Celsius scale links directly to the Kelvin scale used by all chemists.
A change of one degree Celsius is exactly the same size as one kelvin. This shared size makes converting between the two temperature scales very simple. You just add or subtract the number 273.15 to move between them.
A common student misconception is that 0 °C means there is no heat energy left. True zero energy only happens at absolute zero, which sits at -273.15 °C.