eat (away) at (someone or something)
1. To continually bother or worry someone. The precarious state of my finances has really begun to eat at me. I'm worried that your critical comments have begun to eat away at Tiffany—she seems very subdued these days.
2. To erode or wear something away. Don't use that harsh cleaner—it will eat away at a soft metal like this.
eat (away) at someone
Fig. [for a problem] to trouble someone constantly. The nasty situation at work began to eat away at me. Nagging worries ate at me day and night.
eat (away) at something
Fig. to erode something. The acid ate away at the metal floor. Fingers have a mild acid that eats at the metal of the door handle.
eat away at
Destroy gradually, erode; also, worry one constantly. For example, The sea has been eating away at the outer banks for years, or The fact that he failed the test is eating away at him. [Early 1800s]