Terrigender is "a terrier doglike gender, or a gender influenced by or compared to terriers in some way." It is a xenogender and subset of canisgender. It may also be considered a kingender.
The term was coined by Tumblr blog xeno-aligned on April 17, 2019, along with a collection of other canisgender subsets. The flag was released in the same post. Many canisgender flags have a pawprint in the center, which is also a feature of this flag.