I have been learning scottish gaelic. As a former latin student, I knew learning dead or niche languages could contribute to your life experience in unexpected ways. However, I did not expect to have so much fun learning scottish gaelic. You find so much:
French sounds
You can find some french-sounding things like "an-diugh", which reminded me of "aujourd'hui". I don't know if they're related, but it would make sense: French is a celtic language.
Irish gaelic
They seem somewhat similar. I started learning scottish gaelic purely because I am interested in scotrish culture, so I didn't know how similar both languages were.
English
So much is obvious. Some words, like "sgiort" (skirt) or "Tìoraidh" (bye, "cheerie") sound vaguely similar.
Maybe I'll find even more similarities soon! Anyway, I urge you to learn a new language... TODAY.