Pénombre translates to "gloom" or "semi-darkness". It's a more evocative and poetic word than simply "darkness" (obscurité), suggesting a soft, lingering shadow rather than complete absence of light.
In "Chambre 12," Louane uses this word to set a melancholic and intimate atmosphere right from the opening line: "Dans la pénombre chambre 12" (In the gloom, room 12). It immediately draws the listener into the song's reflective and somewhat somber mood, making it a memorable and interesting choice.
Louane sets the whole song inside one motel room, replaying a night that's already over. "Dans la pénombre chambre 12" ("In the dimness of room 12") opens on rain and a bed built for two that she's lying in alone: "J'voyage solo, sur mon lit double" ("I travel alone, on my double bed"), while she admits "C'est sa belle ombre que j'épouse" ("It's his beautiful shadow that I marry") — she's married to a memory, not to him. She says she believed in it the way you believe in God, "J'y ai cru comme on croit en Dieu," and that line sets up the chorus's real trick: "pour te dire adieu" (goodbye) keeps stuttering down into its own hidden "dieu" (God), as if every goodbye she repeats is also a small loss of faith.
The second half pulls the camera back from her own story to the room's: "Même la poussière chambre 12" ("Even the dust in room 12") has seen this before, watching taxis pass the window while other couples' romances start and end the same way — "Les histoires s'écrivent puis s'effacent" ("Stories are written and then erased"). Room 12 isn't really about one relationship; it's the room that outlives all of them, and Louane's goodbye is aimed as much at the place as at the person.