The French idiom “passer au caviar” means literally “to pass to the caviar” or “to switch to the caviar.”

This expression comes from Russia. Under the rule of Tsar Nicholas I (1825-1855), censorship was common. In books and journals, areas that had been censored were covered in black ink. This black ink was the same colour as caviar, which is also black.

Since the early 20th century, this expression makes the connection between the black colour of caviar and the black ink of censorship. There is even a French verb “caviarder,” which means “to redact,” “to censor” or “to black out.”

The equivalent English expression is “to black out.”