Francium is the second rarest naturally occurring element. It’s an alkali metal and generally degrades by decay into astatine. It shares many properties with Astatine and caesium and can form similar salts to both. Its instability makes it if little practical use. Francium was discovered in France (hence the name) in the Curie Institute. It originally has the name Eka-caesium.
French hens are a domestic food animal that, may or may not have originated in France. The name has stuck, and so it gets tied with Francium.
Radium is a naturally occurring radioactive element in alloys of Uranium, and very rarely in Calcites. It’s the most infamous application was in watch and clock diles to make them glow in the dark over long periods. This practice led to the horrendous treatment of the Radium Girls, who were instructed to use their mouths to point the paintbrush. This led to radium ingestion, which acts like calcium in the body and deposited into bones eventually causing cancer. It also helped (along with polonium) to cause madam Curies death.
Skates are Rays that are generally smaller in size, they are slippery and able to fit in small spaces. Thus I tied them to the equally slippery Radium.