A simple little word for a common little fella. Yet, the origin is unknown (*or not?*). Both *OED* and *Etymonline* are bold enough to say "of uncertain origin"; but, of course, they try to explain the etymology of *rat* with *Latin, Romanic, Germanic, Celtic and Greek* connections. [*Etymonline*][1] summarizes in the first paragraph as below: > late Old English *ræt* "rat," of uncertain origin. Similar words are found in Celtic (Gaelic *radan*), Romanic (Italian *ratto*, Spanish *rata*, French *rat*) and Germanic (Old Saxon *ratta*; Dutch *rat*; German *Ratte*, dialectal *Ratz*; Swedish *råtta*, Danish *rotte*) languages, but connection is uncertain and origin unknown. In all this it is very much like *[cat][2]*. <sub><sup>*(a hint for the next question: cat!)*</sup></sub> *Etymonline* gives its own opinion also and includes the dispute between big names: > - Perhaps from Vulgar Latin * *rattus* - **Weekley** thinks this is of Germanic origin, "the animal having come from the East with the race-migrations" and the word passing thence to the Romanic languages - **American Heritage and Tucker** connect Old English *ræt* to Latin *rodere* and thus PIE * *red-* "to scrape, scratch, gnaw," source of *[rodent][3]* (q.v.). - **Klein** says there is no such connection and suggests a possible cognate in Greek *rhine* "file, rasp." - **Weekley** connects them with a question mark and **Barnhart** writes, "the relationship to each other of the Germanic, Romance, and Celtic words for *rat* is uncertain. - **OED** says "probable" the rat word spread from Germanic to Romanic, but takes no position on ultimate origin. The connection to the origin of *rodent* (Latin *rodere* "to gnaw, eat away," from PIE root *red-*) stands out but not favored by *Klein* and *OED* and it is mentioned as an uncertain connection. <sup> <br>(Related question: http://english.stackexchange.com/questions/156079/what-do-rodents-do/156085#156085)</sup> *[OED][4]* goes deeper into the rathole and gives a detailed etymology; and includes the below reasons for the uncertainty: > - It is uncertain whether the Latin and Romance words are cognate with the Germanic words, or whether they were borrowed from Germanic, or vice versa; **in any case the ultimate origin is uncertain; perhaps imitative of the sound of gnawing.** - None of the Latin and Romance words is attested before the end of the first millennium, and the fact that the German word has not undergone the High German sound shift suggests that the Germanic group is also late (Middle High German *ratz , ratze* , German regional (chiefly southern) *Ratz , Ratze* are secondary, perhaps hypocoristic formations). - The word was probably spread with the reintroduction of rats to Northern Europe during the Viking Age (for a discussion of the physical evidence compare P. L. Armitage in Antiquity 68 (1994) 231–40). - A derivation < an ablaut variant of the Indo-European base of classical Latin *rōdere* to gnaw (see rodent adj.) has been suggested, but seems unlikely in the light of the apparently recent introduction of the word. - A suggested derivation of the Romance words < classical Latin *rapidus* rapid adj. is no longer accepted, as it would only account for the Italian, which for chronological and historical reasons cannot be the single origin of the whole group. But, I didn't stop ratting there and checked historical records that include the word "rat" and found the oldest etymological and lexical references as below: From "An universal etymological English dictionary" *By Nathan Bailey* (1731): ![enter image description here][5] <br> <sub>[*(obsolete)* Teut. -> Teutonic -> Germanic]</sub> From "A dictionary of the English language : in which the words are deduced from their originals, and illustrated in their different significations by examples from the best writers : to which are prefixed, a history of the language, and an English grammar" *By Samuel Johnson* (1766): ![enter image description here][6] And the rat-hunting went on an' on and I ended up with the *[brown rat][7]* (and its etymological origin) which is one of the best known and most common rat. It is named *Rattus norvegicus* (Norwegian rat) which is a misnomer because the English naturalist John Berkenhout gave the binomial name, believing it had migrated to England from Norwegian ships in 1728 (which is disproven later.) Towards the end of 19th century, the etymology of *brown rat* was better understood and the below note is mentioned in "Natural History" *by American scholar Alfred Henry Miles*: > The brown rat is the species common in England, and best known throughout the world. **It is said to have travelled from Persia to England less than two hundred years ago** and to have spread from thence to other countries visited by English ships This finding gives a hint that the origin of the word *rat* might be of *Persian* origin (and also *Sanskrit*)[ \[Wiktionary][8] puts as "Middle Persian *randītan* (“to scrape, smooth”), Sanskrit *rádati* (“he gnaws, cuts”))."] Also mentioned in "The Oxford Introduction to Proto-Indo-European and the Proto-Indo-European World" *By J. P. Mallory, D. Q. Adams*: ![enter image description here][9] However, the *brown rat* ultimately came from central Asia and (likely) China. The pinyin *shǔ* of Han character 鼠 (rat) in Mandarin doesn't evoke anything, though I'm like a rat in a corner at this point. [Although, Sanskrit and Mandarin are from the same geographical region.) In conclusion, *Persian* and *Sanskrit* origin makes sense and it wouldn't be possible to go further back (unless a *Hittite* origin? *Rats!*). Anything more to add? Is it possible to find further clarification? <sub><sup>Sorry, I couldn't think of a fancy title for the question.</sup></sub> [1]: http://www.etymonline.com/index.php?term=cat&allowed_in_frame=0 [2]: http://www.etymonline.com/index.php?term=cat&allowed_in_frame=0 [3]: http://www.etymonline.com/index.php?term=rodent&allowed_in_frame=0 [4]: http://www.oed.com/view/Entry/158382?rskey=GBkPbG&result=1&isAdvanced=false#eid [5]: https://i.sstatic.net/BVczQ.png [6]: https://i.sstatic.net/eFqOY.png [7]: http://en.wikipedia.org/wiki/Brown_rat [8]: http://en.wiktionary.org/wiki/rat [9]: https://i.sstatic.net/n4InO.png