Turnkey (noun)

1. A person who has the key to lock or unlock a prison cell.
2. A solution or service that is ready to use, with all necessary components in place.

Origin:

The term 'turnkey' originates from the word 'turn' meaning to turn, and 'key' meaning key, as in a key to lock or unlock a door. originally, it was used to describe someone who would turn the key to lock or unlock a prison door. by the late 19th century, it was being used in a broader sense to describe something that was ready to use with all necessary components in place.

Examples:

1. The new software package is a turnkey solution that will help streamline your workflow.
2. A turnkey investment is a property that is already fully developed and ready for occupancy.
3. The manufacturer is offering turnkey installation services for their latest product.
4. Our turnkey business solution includes everything from setup to marketing support.
5. As a turnkey contractor, the company provides full construction services from design to finished product.