Why celsius scale gives negative temperature?

When the Celcius (Centigrade)scale was set up , it deemed freezing point of water at zero (0 oC) and the boiling point of water at 100 oC.

This is a 'hangover' from the French Revolution of 1789, when the revolutionaries made everything into multiples of 'ten'.

The came Lord Kelvin. He used the same scale , but calculated a temperature of ' O K'. (-273 oC) to be the point were molecular motion stopped.

Helium gas freezes at 6K ( -267 oC ) and solidifies at 4K ( -269 oC).

The units of the Celcius Scale are ' --- oC'. However the units of the Kelvin Scale are ' ---K'. NO degree symbol 'o'.