Taxonomic designation like Rattus rattus

• Pulled — hard — leg of the setter about taxonomic term
• Scientific name involving a repeated word

Wikipedia Word definitions in Wikipedia
A tautonym is a scientific name of a species in which both parts of the name have the same spelling, for example Bison bison . The first part of the name is the name of the genus and the second part is referred to as the specific epithet in the International ...

Wiktionary Word definitions in Wiktionary
n. (context biology informal English) A binomial name consisting of the same word twice, such as ''Bison bison''.