Tripot literally translates to "gambling den" or "dive". It's a somewhat old-fashioned and evocative word that immediately sets a scene of illicit activity and a slightly seedy atmosphere.
In the song, Aznavour uses it to describe the place where he was led astray to play poker, highlighting the unsavory environment that ultimately leads to his downfall and arrest. It's a memorable word that captures the essence of the song's narrative.
"Poker" is a comic story-song. Aznavour plays a young man who gets talked into a card game by three guys from his neighborhood, in a smoky back room over drinks.
The song walks through the game itself: shuffling, cutting, dealing, discarding, and the tense standoffs of trying to read the other players. He bluffs his way into a big pot, thinks he has won with three ladies, only to lose to an opponent holding three kings. Furious, he tears up his cards and throws them down.
Just as he is about to leave, the police raid the place. He ends up in front of a magistrate, who hands him a strange sentence: instead of prison time, he is put to work sorting and filing paperwork, i.e. handling "cards" of a different kind. The song closes on that ironic twist, all because of one bad night at the poker table.