It's a reference to the sci-fi book The three body problem by Liu Cixin[1]. In that ta mysterious game about an alien planet where its population can be dehydrated to survive harsh conditions which could last millenia, and then re-hydrated when the conditions are right.
Although i think the terms hydrate-dehydrate are not unheard of in tech stacks for example in a django REST framework called tastypie to denote serialization-deserialization of data.
Yeah it's a pretty widely used term. ReactDOM has a hydrate() method[0] used to display something on the frontend that has already been rendered by the backend.