Celts and Saxons are actually some of the first migrants into early Europe. They also brought a lot of technology, such as it was. Farming, metal working, etc. Also being somewhat larger than Europeans at the time, they were a thing to be feared. Hitler’s vaunted “Aryan race” was not actually a race, showing that he was either stupid or a liar or both. They were connected by a common language, nothing more, from somewhere farther east.
Assyrians.......................
The closest to such as thing (i.e. meaningful both genetically and linguistically) are the Indo-European peoples, which are basically all non-Semitic Caucasians. By this standard, Celts, Slavs, as well as Iranians and northern Indians are just as "Aryan" as the Germanic tribes.