Deeply wound or distress, as in His criticism cut her to the quick. This phrase uses the quick in the sense of a vital or a very sensitive part of the body, such as under the fingernails. It also appeared in such older locutions as
touched to the quick, for “deeply affected,” and
stung to the quick, for “wounded, distressed,” both dating from the early 1500s. The current expression was considered a cliché from about 1850 on.