In historical linguistics, Italo-Celtic refers to the observation that the Italic languages and the Celtic languages share a number of common features unique to these two groups. These are usually thought of as innovations which are likely to have developed after the breakup of Proto-Indo-European, though it's also possible to argue that some of these aren't innovations, but rather shared conservative features. There's therefore some controversy about the nature of the historical causes of these… (More on Italo-celtic)