warmer

noun3

1. •
   Something that warms (something else) by providing some small amount of heat, such as a hot water bottle or a soup.

   • […] tortillas are kept warm and moist in an electric warmer […] — 1993
2. •
   A piece of clothing for warmth via insulation of body heat.
3. •
   An introductory activity, for example in a lesson, to stimulate interest in a topic.