속이 타요 · 속이 탔어요 · 속을 태우다 (to make someone anxious)
to be anxious, to be worried sick, to be on pins and needles
Example
아이와 연락이 안 돼서 속이 타요.
I can't reach my child, and I'm worried sick.
Word parts
타다 = to burn; literally 'one's insides burn' with worry.