>>20661076none will ever know for sure.
The fall of Troy dispersed the Merari (Sons of Levi) who I personally believe eventually became the Celtic races you mentioned. Again this is my own personal opinion. The histories of men are veiled by the Dragon's mist, if you catch my drift.
You will discover the Testament of Levi here.
https://sacred-texts.com/chr/apo/index.htm I find these books helpful, though none can dispute they could possibly be ((forgeries))