Nuts and Bolts: soubriquets.

 (You can write this word sobriquet if you like.)

A soubriquet is an assumed name, or nickname, that is also in some way descriptive.

Harpo is a soubriquet; Zeppo isn't; Groucho might be. 

The Swan of Avon isn't a soubriquet, either (and why Shakespeare is named after a creature which is famously silent I do not know and cannot imagine).

The English king Henry VIII was called Old Coppernose, which probably counts as a soubriquet even though Henry VIII didn't have a copper nose. Henry VIII put loads of copper into England's coins to make them cheaper to make, so Old Coppernose describes the king's economics, though not his looks.

Soubriquets have been around more or less forever. The Roman emperor Caligula's name was actually Gaius. Caligula means little boots, and he was called that because, when he was a child and still cute, Caligula did indeed strut around in boots just like his soldier dad's.

Soubriquets are found all over the world. One of Mohammed's companions was called Abu Hurairah, Father of Cats, because he was always accompanied by a cat; Mohandas Gandhi is known as Mahatma, which means great-souled; the present president of Zimbabwe, Emmerson Dambudzo Mnangagwa is known, much less affectionately, as The Crocodile.

Still, perhaps even that beats the soubriquet of the poor Viking Eystein.

He was known as Eystein Foul-Fart.

Nuts and Bolts: soubriquets. People are still arguing about the origin of this word. Some say it comes from the two French words sot, foolish and the Italian bricco, knave. Some say that it comes from soubsbriquet, a chuck under the chin.

I can't say that either explanation makes much sense to me.