“9th of october” is about being in a very intense relationship and knowing that you’re bad for each other—you’re ruining each other when you’re in love. When you break up, you’re so angry at the person and don’t want to admit to your own faults. I wrote that song on my birthday two years ago because that’s when everything was falling apart. I originally wrote it as a poem.

• Tove Lo via OUT

In an interview with magazine The Fader, Tove Lo explained:

It started as a poem first. I wrote it on my birthday two years ago when this [relationship I was in] was fully falling apart. I was so angry, so sad, and feeling guilty and betrayed all at once, but I still could see the beauty in what we had. It was like a way to say goodbye to this person even though I never said it.
I went into the studio with the poem and I had the phrasing like, “We never had coffee table books or dinner parties.” We created the chords around the vocals so everything was built after the melody and the phrasing of what was there and not “here’s a track, write on top of it.” It was a while ago since I recorded it. I can hear in my voice what I was going through at the time and it’s so crazy now that I’m in a new place. You can heal if you want to. I’m happy to finally put it out even though it’s like jolting me back into past feelings.