Never speak ill of the dead

Where did the phrase, "Never speak ill of the dead", come from?

It's a very ancient prohibition. In classical Latin it took the form "De mortuis nil nisi bonum", literally "[speak] nothing but good of the dead"; this in turn derived from a 6th-century Greek saying. The earliest English version I know of is a translation from Erasmus: "Rayle not vpon him that is deade". (VSD)