There are cases for all of the names.  The only Easter-y one is “ispanihad”, though, so I’ll focus on that.  The name was, supposedly, used by the Romans and evolved over time.  They would have used it in reference to Spain being overrun by rabbits and also to huge rabbits that were just outside of Spain. Another support of the Romans using a name referencing rabbits for the territory of Spain is that they made coins in Spain that included a rabbit.