keyman

plural keymen

1. datedA telegraph operator.

   Conscious of their importance, the 324 labor delegates marched bravely in and elected by acclaim as their president a onetime Ontario telegraph keyman, Senator Gideon Decker Robertson […]

   1932, Time (volume 19, part 2)

2. IndiaA workman who checks a railway track for faults, and who carries a keying hammer.
3. An employee of vital importance to a business.

   A corporation may feel the need for life insurance on one of its keymen under a variety of circumstances.

   1957, Pearce Shepherd, Andrew C. Webster, Selection of risks

   1 more example

   As the keymen learn how to handle confidential company information, the owner-manager can disclose more to them. In most very small firms, the keymen will be "working" bosses.

   2000, Harvey C. Krentzman, The essentials of business management for profit, page 123