Buttercup

Buttercup is a paper note in Fallout: New Vegas. It can be found. It is the password to Sarah's personal terminal in the Vault 21 gift shop.

Sarah Weintraub’s terminal
Sarah's mail is found on a very hard terminal in the gift shop, and on an easy terminal in her locked room in the living quarters. The terminal in her bedroom can be accessed with the password found on the Buttercup note.