Betula pendula was created in 1788.

Carex pendula was created in 1762.

Well, when you put your finger in between the pendula (the little balls connected to the wire), that stops the flow of energy through the pendula. Newton's Cradle is a device that shows the laws of motion through entertainment. When one pendula is lifted, the the gravity transfers potential energy into kinetic energy, which is sent through the three pendula and to the last one, forcing that pendula to fly up. When the pendula comes back down, it starts the process all over again.

Betula Pendula

"Pendula" isn't of the proper English language.

If you are refering to "Paenula" then the dictionary resault for that is:

a long, circular cloak, sleeveless and often hooded, worn by the poorer classes in ancient Rome.