Songfacts®:

• Baskery is the Swedish trio of sisters Stella, Greta and Sunniva Bondesson. "Catflap" is a British term for a hinged or covered opening in a door that allows an animal (hopefully one that lives there) to come and go as it pleases. Americans know it as a "doggy door" and Swedes call it a "cat door," but the sisters heard "catflap" in the UK and decided to use it in a song.
• In this song, the Bondesson sisters take a feline role, looking for a catflap that will let them inside. It's a feminist message and one of determination. In a Songfacts interview with Sunniva, she explained: "We wrote it when we lived in a little area in Nashville which is not the best area. It was the southwest area, and not the best neighborhood. We had a lot of stray cats around, and we were inspired by them because they're adventurous creatures. So, we used that to describe the feeling of how we found it so hard to crack the music industry. But there's always a way in, and the way in could be the smallest hole, such as the cat door."
• There is some wordplay going on here, and it's intentional. The title is meant to sound like "shut the f--k up."