Back to explorer

entry

rat

/ræt/

A rodent; a betrayer or informant

From O.English, from Proto-Germanic; ultimate origin uncertain rat (A rat or rat-like animal).

noun
verb
rat
Proto-Indo-European (proposed)
Verified
*Hreh “to gnaw, scrape, scratch”
reconstructed
A disputed ancestor connected by some scholars to gnawing and scraping.

from Proto-Indo-European *Hreh₃d- (“to gnaw, scrape, scratch”). However, the rat may have been unknown in Northern...

Proto-Germanic (reconstructed)
Verified
*rattaz, *rattō “rat”
reconstructed
The proposed Germanic source; its exact animal reference is uncertain.

from Proto-Germanic *rattaz, *rattō (“rat”), of uncertain origin, possibly

Old English
Verified
ræt, rætt
The early English word for the rodent.

from Old English ræt, rætt

Middle English
Verified
raat, rat, ratt, ratte
Spelling varied; ratton also appeared through Old French influence.

from Middle English raat, rat, ratt, ratte, rotte

Modern English
rat

A rat can enter English through a fog of uncertainty: Old English had ræt, but nobody can say with confidence where the word began. One leading theory links it to the reconstructed Proto-Germanic *rattaz and, farther back, a proposed Indo-European root meaning “to gnaw, scrape, scratch”—a wonderfully dental etymology for an animal that can chew through wood, wiring, and apparently your peace of mind. Another theory imagines a Vulgar Latin *rattus spreading into Romance languages, while some scholars reject any connection with the gnawing root altogether. By the 1620s, “rat” had acquired its human sense because people believed rats abandoned a sinking ship or collapsing house before everyone else; in 1902, it specifically meant a traitor or informer. So every time someone “rats” on a colleague, the insult carries an old image: tiny paws already racing away from disaster.

§