*bheid-

The core idea of this root was:

splitting

This is still visible in words like boat, which were made from splitting wood, but the main branch of the family in Germanic language is about biting (“splitting with teeth”).

• to bite
• bit (“small part bitten off”)
• bitter (“biting taste”)
• bait (“makes you bite”)
• beetle (“biting insect”)

The root is also the origin of the word pita (the bread) and pizza.
Also the Latin based fission belongs here, which is still about splitting.