Buttercup (genus Ranunculus)   Depending on the source, there are some 200 to 600 species of Buttercups, in the genus Ranunculus, They have shiny yellow petals and when alive they are poisonous to humans. When dry, they are not. You mat remember holding a Buttercup under a friend's chin and if there was a yellow reflection of the flower, assumed your friend liked butter. Michael Avenatti ,on 29 July 2018, said "You better buckle up, buttercup" in a tweet addressing Rudy Giuliani.