1. Rigging. According to the Encyclopedia Britannica:
The idea is that the clevis pin will take all the load, while the cotter holds it in place. Also because the pin is round whatever it in pinning together have the ability to spin freely around the pin (unless secured elsewhere of course) thus allowing to truss configurations that are not just straight lines.
Commonly used in rigging in conjunction with forks and spigots to connect truss sections together.
Often an R-Clip is used as the cotter pin.
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2. Common male name in the South. "This is Clevis and his wife and cousin BettySueAnnRachelStephanie."