What is darn it?

"Darn it" is an exclamation used to express irritation, disappointment, or an unpleasant surprise. It is a relatively mild swear word, often used in place of more offensive language. The phrase "darn it" originated in the United States in the late 19th century as a euphemism for "damn it." It has since become a common expression in English-speaking countries. The phrase was originally used by fabric makers to refer to mending holes in clothing with a stitch called a "darn," hence the use of the term "darn it" as a call to fix or repair something.