from The Century Dictionary.
- noun The typical genus of swifts, of the family Cypselidœ and subfamily Cypselinœ, having the hind toe versatile and the tarsi feathered. There are numerous species, chiefly of the old world. C. apus is the common swift of Europe.
Sorry, no etymologies found.
It has already been stated that the footless bird, which some term the cypselus, resembles the swallow; indeed, it is not easy to distinguish between the two birds, excepting in the fact that the cypselus has feathers on the shank.
The swift (cypselus) is ordinarily classed with the swallow, which it resembles in its flight, habits, and migration.
The Greeks had a double idea in the word, which it is not the least necessary to keep; and Aristotle's cypselus is not the swift, but the bank-martlet -- "they bring up their young in cells made out of clay, _long_ in the entrance."