waterphone

A musical instrument consisting of many metal bars connected to a disk with a metal underside. The metal bars are played with either a bow or a stick by either sliding over or tapping them, while the metal underside of the disk is played by patting one's hand against it.
This instrument is most commonly used for the soundtracks or horror movies.

Person 1: That high-pitched echo always sends a shiver down my spine.
Person 2: Did you know those are made with waterphones?
Person 1: Dafuq's a waterphone?

Illuminati

A former organization from the last century, consisting of scientists that wanted to escape from the (at the time) strictly religious outside world. After science became a subject to freely discuss in public without danger, the Illuminati disbanded.
Its name was based on the verb 'to illuminate', due to the members of the former group seeking enlightenment about the world.

In recent years, people started claiming that the Illuminati is some sort of conspiracy order/deity rising to, if not already at, total control of the world.
Said people also claimed the eye within a triangle (the Owl's Eye) found on dollar bills is an "All seeing eye", that is found within any shape that could be seen as a triangle, or anything that could end up with 3 (due to triangles having three sides), no matter how indirect.

Conspiracy theorist: "Illuminati is everywhere! It's controlling us all!"

Random bystander: "Not sure if that guy is desperately trying to be funny, or actually stupid."