Kelnidide was a material used in the construction of Federation space stations in the 24th century.

Starbase Deep Space 10 was designed to have a kelnidide core with a thickness of 15.75 centimeters. Contractor Kesla Randu instead made this 16 centimeters, at no extra cost, because it was easier for her manufacturing facilities. The increased mass of the station contributed to the severity of an atmospheric systems failure in 2377. (CoE eBook: Troubleshooting)

This was likely intended to be a reference to the material kelindide.