Evidence for a connection:
* Indoeuropean origin: Both Germanic and Celtic languages belong to the Indo-European language family. This means they share a common ancestor, estimated to have been spoken around 4,500 years ago.
* Similar vocabulary: There are some shared vocabulary items, particularly in older forms of the languages, indicating they diverged relatively recently within the Indo-European family.
Evidence against a closer connection:
* Different branches: Germanic and Celtic languages belong to separate branches of the Indo-European family tree. Germanic languages are part of the Germanic branch, while Celtic languages make up the Celtic branch.
* Significant divergence: Despite their common ancestor, Germanic and Celtic languages have undergone substantial independent development over millennia, resulting in significant differences in grammar, phonology, and vocabulary.
* No "proto-Celto-Germanic" language: There is no evidence of a single ancestor language directly connecting Germanic and Celtic, unlike, for example, the shared Proto-Germanic ancestor of all Germanic languages.
In summary:
While Germanic and Celtic languages share an ancient Indo-European ancestor, they are not directly related in a way that would make them "sister languages." They are more like cousins, having diverged sufficiently to have become distinct branches of the Indo-European family.
Further points to consider:
* Subgrouping within Celtic: The Celtic branch itself is divided into various sub-branches (Insular Celtic, Continental Celtic), which have further diverged.
* Borrowing and contact: Historically, there has been some contact and borrowing between Celtic and Germanic languages, particularly in areas of historical interaction. This can sometimes make it difficult to distinguish shared ancestry from later influences.
The relationship between Germanic and Celtic languages is a subject of ongoing linguistic research.