I was about to post that I had only heard the phrase in a British context, but then I realized that, growing up Presbyterian, I’ve never spent much time around denominations where clergy wore the collars. For all I know, it could be very common among other religious circles. A nice example of how personal perspective can skew one’s perception of where a word or phrase is used.
Right, we in the more Reformed and low church traditions tend not to wear them though that’s not universally true. I did note that a female Lutheran pastor on that same Good Friday walk was wearing the “dog collar.”
The dog collar usually refers to the full piece of plastic attached to a specially designed shirt with metal studs and not the “tabbed” collar that is made to look like the priest is wearing a cassock. Generally speaking, here in the US, Roman Catholic priests tend to wear tabbed collars and Episcopalians and Lutherans wear dog collars. I own a tabbed collar shirt from the days when I visited prisons. I don’t do much of that anymore. And hospitals require their own name plates these days for us to get any private information on those whom we are visiting. The collars won’t get us that information.
Edited for typo.