Fonce-dé is a French slang term that means "stoned" or "high" from drugs, particularly cannabis. It's a verlan word, which is a type of French argot where syllables of a word are inverted.
In the song, the artist sings, "Dans ma fonce-dé, j'perds mon feu" (In my high, I lose my fire), indicating a state of being heavily under the influence. This word is interesting because it's a common slang term in French hip-hop culture and provides insight into informal language use.
"Royal" gets its name from a big hand-rolled joint that Benab lights up right in front of the cops, a small act of defiance the whole song keeps circling back to. Between verses, the chorus repeats that same picture: roll two, light the royal, and lose track of time.
Underneath the swagger, the verses paint a rougher scene: driving through rough neighborhoods, staying on guard, and the risks that come with fast money and the wrong crowd. It plays less like a celebration and more like a snapshot of a life lived on edge, held together by that one repeated smoke break.