How to spell celsius

I note that the Oxford English dictionary now uses “Celsius“, as do Americans and the man’s name is “Celsius.” However, it was always “Celcius” when I was at school and University. I’ve checked with others and they recall being taught the alternate spelling.

: relating to or having a thermometer scale on which the interval between the freezing point and the boiling point of water is divided into 100 degrees with 0 representing the freezing point and 100 the boiling point.