Cavale literally means an 'escape' or 'flight', often used to describe a prisoner who is on the run. It's a dramatic and slightly edgy word that you won't hear every day.
In this song, Coeur de Pirate uses it in a beautiful metaphor: "mon coeur partait en cavale" (my heart was going on the run). This paints a vivid picture of her feelings as wild, unstoppable, and breaking free, adding a powerful layer of emotion to the story.
This song is a fantastic look back at a one-sided crush. Coeur de Pirate remembers trying so hard to get someone's attention, even traveling for hours just to see them. She sings about putting on glitter to get noticed, "mettre des paillettes, me faire remarquer" (putting on glitter, getting myself noticed), while this person was so popular that others were shouting their name from afar. It's a classic story of being completely into someone who seems totally out of reach and maybe a little cold, like "une montagne au centre des marées" (a mountain in the middle of the tides).
The whole story flips when the other person realizes how much she likes them. As soon as they knew her heart was running wild for them, "mon coeur partait en cavale" (my heart was on the run), they took off. The song then becomes a series of sharp questions for this person, wondering what they'll do "Quand les regrets reviendront?" (When the regrets come back?). The final verse is the best part: they meet again, and the other person now seems full of regret, realizing they missed their chance. It's a perfect revenge fantasy about the one that got away... and then wished they hadn't.