Vagile comes from Latin vagus ('wandering, roving') plus -ile; a biological term for organisms able to move about and disperse freely. The historical chain includes Latin vagus. The quoted older sense, "wandering, roving," supplies the immediate semantic anchor for vagile. The formation is best read as borrowed: the word vagile carries its older form-history into a compact English lexical shape. In present English it is used as a adj, "able to move about freely and migrate; not fixed in place (of an organism)". English derivatives include vagility; related English forms include vagrant, vagary, vague, and vagabond. The result is a adj whose etymology preserves both the older form and the later English specialization.