Note that the caret (‸) and circumflex (^) are different signs. The caret is used across plenty Latin orthographies to convey that something is missing, as its name implies; while the circumflex is a diacritic usually going over the letters, whose function depends on the orthography of the language in question.
EDIT: as for the etymology of circumflex it's basically Ben Dover "bent around" (circumflexum).