Question

why solid carbon dioxide is called 'dry ice' ?

Answer 1

because when the CO2 is below -110 F
the co2 changes into solid form
When it is warm, it means just a bit more than --110 F it changes into its gaseous form.
that means co2 can't be in liquid form for a long time.
That's why it is called dry ice

Answer 2

basically when carbon dioxide ( co2) which is in the form of GAS,
when we compress this co2 gas it becomes DRY ICE which looks in solid
- ice form. therefore this compressed form of co2 is known as " dry ice " .