Packard said:
I have one of those too.
I read long ago how the name “church key” came to pass. The inventor was a man named “Church”. And he had a company called the “Churchkey Can Company”.
There are some other explanations going about, but this one seemed most plausible.
https://en.wikipedia.org/wiki/Churchkey_Can_Company
"Definition of Church Key
A Church Key, also known as a bottle opener or can opener, is a device used to open beer and soda cans, as well as bottles with corks or caps. The term “Church Key” originated from the resemblance of early bottle openers to old-fashioned church door keys. These early openers, dating back to around 1900, had a similar shape and design to large, ornate door keys used in churches.
Evolution of the Term
Over time, the design of bottle openers changed, but the name “Church Key” remained. The term is now used to describe various types of openers, regardless of their shape or functionality. The name is thought to have been transferred to the new can opener design, which makes triangular marks in beer cans, as a humorous nod to the earlier bottle opener’s resemblance to a church key.
Theories Behind the Name
Several theories have been proposed to explain the origin of the term “Church Key”:
Satire and Prohibition: One theory suggests that the name was meant as a satire to the proponents of Prohibition, implying that drinking beer was an “unchurchly” activity.
Missed Church: Another theory proposes that the name refers to the idea that someone using a Church Key (bottle opener) would likely miss church, as they would be too busy drinking beer.
Resemblance to Church Door Keys: The most widely accepted theory is that the name simply refers to the early bottle openers’ resemblance to large, ornate church door keys.
In Conclusion
A Church Key is a device used to open beer and soda cans, as well as bottles with corks or caps. The term originated from the resemblance of early bottle openers to old-fashioned church door keys and has evolved to describe various types of openers, regardless of their design or functionality."
Also -
https://advancedmixology.com/blogs/art-of-mixology/what-is-a-churchkey-opener. 
