Linguistics explanations and predictions often are testable. The wug test is a famous example. For historical linguistics, yes, you can't summon new historical

Linguistics explanations and predictions often are testable. The wug test is a famous example. For historical linguistics, yes, you can't summon new historical evidence out of the void, but you still have a huge amount of existing evidence to work with, and you can always go looking for that which has been overlooked: you have the entirety of written history at your disposal.