Opabinia is a freaky sea creature of the Cambrian age (Dutch: Cambrium) with some special properties like 5 eyes and a grasping 'snout'. I liked the sound of the word, and picked other Cambrian animals like Pikaia and Hallucigenia for my other kitties. But long names tend to be turned into a shorter version, creating: Pika, Hallu and Opa (which means gramps in Dutch).