Phalangium Opilio is a scientific name for a common species of daddy long-leg spider. As this name is a tongue-twister for some, people often search for various synonyms of this term to find more information about the creature. Some common synonyms of Phalangium Opilio include harvestman spider, cellar spider, daddy long-legs, and granddaddy long-legs. However, it's important to note that while these names are used interchangeably, not all of them represent the same species. Harvestman spiders are a different group of arachnids, while cellar spider refers to the family of spiders that Phalangium Opilio belongs to. Nonetheless, all of these names can help people identify and learn more about these fascinating, leggy creatures.