Fake Dutch (of sorts)
In an interview for Telle est la télé !, a French-speaking newsblog with a focus on movies & TV, director Jean-Pierre Jeunet hinted at the ragmen (or Bazil, at least) speaking some kind of a "fake Dutch":
Et qu’est-ce qu’il [Dany Boon] a pu apporter par rapport au personnage car c’est vrai que quand vous créez le scenario, vous avez tout dans la tête, c’était peut être pas facile d’apporter des éléments supplémentaires ?
Que ce soit Jamel [Debbouze] ou lui, ils viennent de la scène, ils ont une grande faculté d’improvisation et de trouver des idées. C’est donc plein de portes ouvertes dans certaines scènes où je lui proposais : « Voilà ce qui se passe, qu’est-ce que tu ferais toi ? ». Alors des fois j’avais vu une petite idée, j’avais revu ces spectacles en vidéo je savais que je pouvais l’amener à faire du faux hollandais, un faux langage. Mais je le poussais pour qu’il trouve lui l’idée. Et puis parfois quand il faisait son geste avec les doigts qui est absolument incroyable, ça ne pouvait venir que de lui, je n’aurais jamais pensé à imaginer ça. Je ne l’avais pas vu avant donc ça ce sont des cadeaux qu’apporte l’acteur.
Interview de Jean-Pierre Jeunet pour le film "Micmacs à tire-larigot", Franck Peltier for Telle est la télé !, October 27th, 2009
Translation improved from DeepL:
And what did he [Dany Boon] bring to the character? Because it's true that when one creates the scenario, you have everything in your head, it may not have been easy to bring additional elements?
Whether it's Jamel [Debbouze] or him, they both come from the stage, they have a great ability to improvise and find ideas. So there were a lot of open doors in some scenes, where I suggested, "This is what's going on, what would you do?". So sometimes I had a little idea, I had seen his shows again on video, I knew I could get him to make fake Dutch, a fake language. But I was pushing him so that he was the one to come up with the idea. And then sometimes he made his gesture with his fingers which is absolutely incredible, it could only come from him, I would never have thought of that. I hadn't seen it before, so they're gifts brought by the actor.
Interview de Jean-Pierre Jeunet pour le film "Micmacs à tire-larigot", Franck Peltier for Telle est la télé !, October 27th, 2009
As to the "significance of them speaking that way", while I didn't find any interview talking about this particularly, it would simply appear as one of the many ways used in the movie to depict the group as "non-conformists". You might want to notice that the summary available on the director's website mentions the following points:
Bazil and the group are a band of "hurluberlus", which, according to the Larousse dictionary, is a term for
Familier - Personne étourdie, écervelée qui se comporte avec extravagance.
Informal - A dizzy, empty-headed person who behaves extravagantly.
thus emphasising the group's "unusualness".
the "spirit" of the movie is similar to Bibi Fricotin's kind of fantasy. Bibi Fricotin is one of the many French comics of the first half of the 20th century with lots of "funny" names, similar to the "fake Dutch"'s alleged nonsense.
