Yours, Etc.: Origins and Uses of 8 Sign-Offs
early 15c., from Middle French confidence or directly from Latin confidentia, from confidentem (nominative confidens) "firmly trusting, bold," present participle of confidere "to have full trust or reliance," from com-, intensive prefix (see com-), + fidere "to trust" (see faith). For sense of "swindle" see con (adj.).