tautonym

noun

1. A binomial name consisting of the same word twice, such as Bison bison.

   “And that would mean a species named Leucanthemum leucanthemum, with the genus and species epithet the same (a tautonym), which is a total no-no in botany.”

2. A word or term made from two identical parts or syllables, such as bonbon or dada.

   “The chapter on reduplication - "flip-flopping higgledy- piggledy through the riffraff" - differentiates rhyming compounds like bigwig, hotshot, ragtag, sci-fi from repetitions called tautonyms, such as bye-bye, so-so, rah-rah, as well as from ricochet words in which the repeated element is modified: chit-chat, roly-poly, shilly-shally.”

3. An absolute synonym.