There is a difference between תנור (oven) and כירים (stove): כירים only cooks what is resting on the fire and in the pot that is placed upon it for cooking. And it is called כיר from the language of fire. And the name for pairs כירים is used when there is space for two pots resting. And the name כירים is not used before the heating. But the noun תנור can also be used before the heating.

And moreover, the name כלי חרש (earthenware vessel) cannot be used until it is heated with a light through its creator. And thus, it is also called כלי יוצר (pottery) and before this it is called חומר (material) or טיט (mortar).