sincerus

My college dictionary says that "sincere" comes from French and ultimately from the Latin "sincerus" meaning pure or honest.

Dan Brown's statement to the court tells us how little he knows 2006

The proper spelling would then be _simcerus_, and euphonically _sincerus_: thus we have _sim-plex_, which does not mean without a fold, but (_semel plico_, [Greek: plekô]) once folded.

Notes and Queries, Number 208, October 22, 1853 A Medium of Inter-communication for Literary Men, Artists, Antiquaries, Genealogists, etc Various 1852