Innerspring (noun)

A coiled or wound spring inside a cushion, mattress, or other support that provides elasticity.

Origin:

From the late 19th century, from inner + spring.

Examples:

1. She slept soundly on her new innerspring mattress.
2. The innerspring provided the necessary support for his back.
3. Innersprings are one of the most popular materials for mattresses.
4. The innerspring was designed to prevent sagging over time.
5. The sofa was comfortable, thanks to its sturdy innerspring.