Être dans les petits papiers de quelqu'un

Literally: To be in someone's little papers

Example: “Depuis qu'il a retrouvé le dossier perdu, il est dans les petits papiers du directeur.” — Since he found the lost file, he's been in the director's good books.

English equivalent: In someone's good books

Origin: The base image is literal: to be in someone's papers, you first had to be written about in them — imagine clearing an attic and finding the sheets on which your late grandfather recorded everything he thought of his housekeeper. Discreet information travels more safely written and sealed than spoken through a messenger, and if what it carries is praise of someone you want a favor done for, you have the whole of the modern sense. It appears at the end of the 18th century as être dans les papiers de quelqu'un. The petits grafted on later, and from a much colder source: petits papiers were intelligence files, sometimes secret, on which a person could be recorded along with an opinion of them. The same thing exists now, more or less officially, in state departments — computerized. What the blend kept from the older form was only the flattering half.