Backbone (noun)

1. The main support structure of an organism, organization or system.
2. The central, most important part of something.
3. The spinal column of a human or animal body.

Origin:

Derived from the old english 'bacbun' meaning spinal column.

Examples:

1. The backbone of the company is its experienced employees.
2. The city's transportation system is the backbone of its economy.
3. The backbone of the computer network provides a secure and fast connection.
4. A strong family is the backbone of a healthy society.
5. The backbone of the vertebrate body is made up of 33 individual vertebrae.