Why is a fresno trowel for concrete called a fresno?

I lived in Fresno for 25+ years, poured quite a few slabs as an amateur, and used fresno floats. I'm English and so asked every pro I met about why it's called a fresno. No one knew. I'll guess therefore, that there's no secret, it was used in Fresno first, or mostly, there's as much concrete there as anywhere. Hardly a fascinating guess but that's the world of concrete for you.
Fresno's a cool place... California's back room, a place where the comfy old sofa is kept.