Proto-Celtic is the reconstructed ancestor of the Celtic languages, believed to have been spoken around 1000 BCE to 500 BCE. It is part of the larger Indo-European language family and is the root from which languages like Irish, Welsh, and Scottish Gaelic evolved. Linguists have pieced together its vocabulary and grammar through comparative analysis of its descendant languages. The spread of Proto-Celtic is associated with the movement of Celtic tribes across Europe, particularly during the Iron Age. As these tribes migrated, they carried their language with them, leading to the development of distinct regional dialects. This historical process laid the foundation for the rich diversity of Celtic languages we see today.