Gee, I didn't know the difference before, so thanks.
![grin =D](http://www.armedpolitesociety.com/Smileys/default/grin.gif)
Note the word "pronounced." It's not very far-fetched to have a distortion like that enter common parlance, especially since "calvary" is and was in much more common use than "cavalry."
According to something I read long ago in a probably long out-of-print book or article, by a probably long-gone author, that was the pronunciation common to a lot of horse soldiers. This source also mentioned that new recruits who used the correct term "cavalry," were subject to derision. There was no reason for the writer to make a joke about something like that, so I took it as authoritative.
That was in the days before the internet introduced its own distortions and information gaps.
![Grumpy Old Man :old:](http://www.armedpolitesociety.com/Smileys/default/oldman.gif)
,
![grin =D](http://www.armedpolitesociety.com/Smileys/default/grin.gif)