cut (one) to the quick

1. To slice a part of the body very deeply. Be careful—one slip of that knife and you'll cut yourself to the quick. I guess he didn't cut himself to the quick after all—the doctor says he doesn't need stitches. Hey, get away from there—that saw could cut you to the quick!

2. To strike the deepest, most fragile part of one. Typically used to describe emotional wounds. I can't even look at her right now—that hurtful remark cut me right to the quick. Even though the comments cut me to the quick, I remained composed and carried on with the lecture. Do not question her ability to parent—that will definitely cut her to the quick.

cut someone to the quick

If something cuts you to the quick, it makes you very upset. The cruelty of their words cut me to the quick. That tone of hers always cut him to the quick. Note: The quick is the very sensitive flesh under the fingernails or toenails.

cut someone to the quick

cause someone deep distress by a hurtful remark or action.

Quick means an area of flesh that is well supplied with nerves and therefore very sensitive to touch or injury.