Gnaw
Gnaw (na) , transitive verb
[Old English gnawen, Anglo-Saxon gnagan; akin to Dutch knagen, Old High German gnagan, nagan, German nagen, Icelandic & Swedish gnaga, Danish gnave, nage. Compare Nag to tease.]
1.
To bite, as something hard or tough, which is not readily separated or crushed; to bite off little by little, with effort; to wear or eat away by scraping or continuous biting with the teeth; to nibble at.
His bones clean picked; his very bones they gnaw.
2.
To bite in agony or rage.
They gnawed their tongues for pain.
3.
To corrode; to fret away; to waste.
4.
To trouble in a constant manner; to plague; to worry; to vex; -- usually used with at; as, his mounting debts gnawed at him.
Gnaw , intransitive verb
To use the teeth in biting; to bite with repeated effort, as in eating or removing with the teeth something hard, unwieldy, or unmanageable.
I might well, like the spaniel, gnaw upon the chain that ties me.