Marigot literally translates to "backwater" or "swamp". It's a less common word that evokes a specific, often murky, image.
In the song, the artist uses marigot to describe a place that is dark and teeming with "cafards" (cockroaches), suggesting a morally questionable or unpleasant origin for the person he's singing about. It adds a layer of intrigue and mystery to the narrative.
Yamê's "Céline" is a wild ride through a whirlwind romance that quickly turns sour. He starts off completely smitten, describing how he "buggé sur toi" [got stuck on you] and how this person, Céline, replaced all his troubles. He feels like a king, "sur mon gros bateau" [on my big boat], even if he doesn't actually own one! She makes him feel good, even if it means he's "sors la carte un peu trop" [pulling out the card a bit too much].
But things take a dark turn. He realizes he was blind to the true cost, feeling it but pretending not to see. Céline, who he thought was everything he wanted, seems to have come from a dark place, "loin dans le marigot où ça grouille de cafards" [far in the swamp where it's crawling with cockroaches]. Now she's selling off what they had, and he's stuck in a "putain d'cauchemar" [f***ing nightmare], trying to sell the ring. When he calls, she doesn't answer, leaving him to wonder, "Qu'est-ce qui va pas chez moi?" [What's wrong with me?] It's a raw look at a love lost and the confusion that comes with it.