How timely. We were just arguing in the office yesterday about the word restaurateur and that "doesn't it have an n in it?" Dave Cook of Eating in Translation must have read our minds, as he posted a link to an explanation of where the n went:
Restaurateur is the noun created from the verb restaurer by replacing the -er ending of the verb with the -ateur ending for for a man (its female equivalent, restauratrice, only appeared in 1767) who carries out the action. Hence, no n. At first, he was an artisan who restored or repaired objects. In the seventeenth century, he was an assistant who set broken bones for a surgeon. In the 1770s he became a man skilled in creating this special soup called a restaurant.
See, [name redacted]? Told ya, so!