Could be that they mean “ass” in the zoological sense - as in something resembling a donkey or horse (for some reason).
The funniest part is they have every right to do this kind of stuff.
https://en.wikipedia.org/wiki/Bony-eared_assfish
The bony-eared assfish may have the smallest brain-to-body weight ratio of any vertebrate.
Poor fish
Like many other creatures that dwell in the depths of the sea, assfish are soft and flabby with a light skeleton. This is likely to have resulted from a lack of food and the high pressures which accompany living at such a depth, making it difficult to generate muscle and bone
TIL I am like the creatures dwelling in the depths of the sea, both flabby and low in muscle mass, but not for lack of food…
and onus could either mean “hake, a relative of cod”, Hanke says, “or a donkey”. Adam Summers, associate director at the Friday Harbor Laboratories at the University of Washington, concurs, saying onus could easily read “as a homonym of the Greek word for ass”.
I love how instead of translating it to being like hake they went with anus.