The other day I was wondering about the etymology of strait and straight. I knew they weren't related, but I couldn't remember where each one came from. Strait was borrowed from French, and it came from the Latin strictus, the past participle of stringere. This root also gives us not only strict but stringent and strain.
Straight comes from an old past participle of stretch, making it analogous to other pairs like teach/taught and catch/caught.