noun
kettle
KET-uhl/ˈketl/
A container used for boiling or heating its contents.
The kettle releases steam through its curved spout.

Etymology
Old English cetil named a vessel for boiling or heating liquids over a flame. The familiar water kettle continues that function, with the smaller tea-kettle sense developing later.
In context
when a kettle boils Suddenly at the boiling point it's not working so well so a well-designed kettle will circulate the water around