When Marguerite Perey named element 87 – then only known as actinium K – in 1946, her first choice was catium, since at that time it was believed that francium was the most electropositive element (hence the derivation from cation). Her supervisor, Irène Joliot-Curie, objected to it because it was more suggestive of cat – and gryphons like Gallus are sometimes called catbirbs, hence his inclusion here. The name Gallus also suggests "Gallic", i.e. France.
On the other hand, MLPFIM has no notable actual cats outside Capper Dapperpaws and Opalescence. So I brought in Yuumi from League of Legends, with a pun about the 22-minute half-life of francium-223 (proof here).
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