The tête à Toto is a French typographical design and children’s game, well known to French schoolchildren, depicted at right. It consists of the equation “0+0=0”, written with the first two ‘0’s for eyes, the ‘+’ for a nose, the ‘=’ for a mouth, and the final ‘0’ surrounding, as a stylized face or skull.
It is drawn while reciting:
Zéro plus zéro égale
la tête à Toto
Translated:
Zero plus zero equals
the head of Toto (Toto’s head)
As his head equals zero, it means that his intelligence is null.
The name, or character, of Toto is a common stock character in French culture; he is the generic child used in jokes ("Toto asks his mom..."). See Blague de Toto (Toto joke).
The term is also used as a circumlocution for "zero", and in prostitution slang for a prostitute, or rather prospective prostitute, who has so far had zero clients; see references at Wiktionary.