Where did the word k-9 meaning dog come from?

The term "K-9" for dog actually doesn't come from the letter "K" standing for "canine." It's a military abbreviation for "canine" used to distinguish dog units from other units.

Here's a breakdown:

* Military Code: In the military, units are often designated with letters to simplify communication and identification.

* K for Canine: The letter "K" was assigned to canine units, likely because it's the first letter in "canine."

* K-9: This abbreviation became widespread, especially in law enforcement and military contexts, to refer to working dogs.

So, "K-9" doesn't directly relate to the dog's physical characteristics or its species. Instead, it's a military code word that has been adopted by various organizations.