ter·ri·er / ˈterēər/ • n. a small dog of a breed originally used for turning out foxes and other burrowing animals from their lairs. ∎  used in similes to emphasize tenacity or eagerness: she would fight like a terrier for every penny.ORIGIN: late Middle English: from Old French (chien) terrier ‘earth (dog),’ from medieval Latin terrarius, from Latin terra ‘earth.’

terrier Any of several breeds of dog. Originally trained to dig out game, they have been used to hunt badgers, foxes, weasels, and rats. When the quarry is located, the terrier(s) is sent down to dig it out of its burrow. Breeds include the Sealyham terrier, fox terrier, and Manchester terrier. Larger breeds, such as the Airedale terrier and Irish terrier, are often used as guard and police dogs.

terrier2 small breed of dog.
So called from its pursuing the quarry into its earth. XV. — early modF. terrier — medL. terrārius; cf. prec.

terrier1 register of landed property. XV. — OF. terrier, sb. use of adj. :- medL. terrārius, f. L. terra land.