I have always wondered where this phrase originated.
A thought I have had is as follows:
I am sure, dear reader, you remember the Old West, where we had cowboys huddled over a night campfire (attempting to keep warm from the bitter cold) and the horses close by (to the cowboys) to deter theft.
Further, you can imagine, the extremely quiet environment.
Should a cowboy sneeze, it would be quite loud.
Seconds before a cowboy sneezed, the cowboy would say “Hold ya’ Horses”.
This was because the loud sneeze would scare the horses.
Thus the phrase…”Hold ya’ Horses”.
Here endith the lesson.
