I borrowed this children's book from a library somewhere before 2009 (most likely before 2007). It was written in French and I wouldn't think it was translated from another language, so it was most likely from a French-language author (although not necessarily from France).
It involved a species of small leprechauns, divided into 4(?) color-coded ranks (I think Reds, Blues, Yellows and Greens), but sharing a same nest. The leprechauns had a "security" system where one of the ranks would choose the weekly/monthly passphrase, which had to be a sentence the initials of which would form a noun. The nest's guards would recite the sentence to anyone wanting to enter, and the incomer would reply with the "secret" noun. (this is obviously a very flawed system, hence the quote marks on "security")
Two keys I remember pretty vividly are:
- "Sortez Avec Les Uniformes Troués", noun SALUT ("Go Out With Holey Uniforms"/HELLO)
- "J'adore (J'Aime?) Ramasser Des Ignames Nourrissants", noun JARDIN ("I Love Picking Filling Yam"/GARDEN)
The rank which came up with the GARDEN passphrase was mocking the rank which came up with HELLO, for a lack of creativity.
The following I'm less sure of: the story may have revolved around one or two kids being shrunk to the leprechauns' size, and trying to go unnoticed (they figured out the passphrase system, I think). As I also remember this book being in the "Neuf - L'école des loisirs" collection, it may have had something to do with the Enfantastiques stories. Also, something about a leprechaun losing his belt?
- Googling the passphrases I remember (between quotes to get an exact match), but literally no results
- browsing what I remembered as the Enfantastiques collection, but nothing obvious came up - and there seems to be way less books than I recall;
- Googling for variations of
l'école des loisirs roman lutins/
l'école des loisirs novel leprechauns/