Man. Folk etymologies. So convincing. So spurious.
My dad was apparently a big fan of the one that claimed that “sincere” comes from the Latin “sin cera,” meaning “without wax”. The claim was that a marble statue that was flawed would have chips and dings filled with a carefully-matched wax fill. But a well-crafted (and presumably honest? I guess?) statue that did not require such patching would be labeled “sin cera”.
Sigh.