[ˈlɪn(t)ʃpɪn], (Noun)

Definitions:
- a person or thing vital to an enterprise or organization
(e.g: nurses are the linchpin of the National Health Service)

- a pin passed through the end of an axle to keep a wheel in position


Phrases:

Origin:
late Middle English: from Old English lynis (in the sense ‘linchpin’) + pin