De mortuis nil nisi bonum

The Latin phrases De mortuis nihil nisi bonum ("Of the dead, nothing unless good") and De mortuis nil nisi bene [dicendum] ("Of the dead, nothing [spoken] unless well (truthfully)") indicate that it is socially inappropriate to speak ill of the dead. As a mortuary aphorism, De mortuis. . . . derives from the Latin sentence ("Of the dead nothing but good is to be said"), which also is abbreviated as Nil nisi bonum. Freer translations into English are often used as aphorisms, these include: "Speak no ill of the dead", "Of the dead, speak no evil", and "Do not speak ill of the dead".

The first recorded use of the phrase of mortuary respect dates from the 4th century, published in the Lives and Opinions of Eminent Philosophers (ca. AD 300), Book 1, Chapter 70, by Diogenes Laërtius, wherein the Greek aphorism τὸν τεθνηκóτα μὴ κακολογεῖν (“Don’t badmouth a dead man”) is attributed to Chilon of Sparta (ca. 600 BC), one of the Seven Sages of Greece. In the 15th century, during the Italian Renaissance, the humanist monk Ambrogio Traversari translated Diogenes’s Greek book into Latin, as Laertii Diogenis vitae et sententiae eorum qui in philosophia probati fuerunt (1433), and so popularized De mortuis nihil nisi bonum, the Latin aphorism advising respect for the dead.

We eat and drink, we come and go,
(The sunlight dies upon the open sea.)
I speak in riddles. Is it so?
My riddles need not mar your glee;
For I will neither bid you share
My thoughts, nor will I bid you shun,
Though I should see in yonder chair
Th’ Egyptian’s muffled skeleton.
One toast with me, your glasses fill,
Aye, fill them level with the brim,
De mortuis, nisi bonum, nil!
The lights are growing dim.

My mother made my need,
my father my conscience.
De mortuis nil nisi bonum.

Therefore it will cost me
bitterly to lie,
to prostrate myself
at the edge of a grave.

I say to the earth
“be kind to my mother,
now and later.
Save, with your coldness,
the beauty we all envied.”

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Wikipedia