Hydrate began as a term for populating an instantiated (but empty) value-object/model from a db, (specifically in Hibernate.)
Various other ORMs and tools like BizTalk use Hydrate and other related terminology, (e.g. BizTalk uses the term Dehydrated to mean an instance is available but not yet populated.)
Personally I'm averse to redundant terminology overhauls, populated means the same thing, without re-inventing language. It adds nothing and leads to confusion (common first thought on encountering re-invented terms: is this somehow different and magical?).
The BizTalk extension of this style of language, specifically Dehydrated is redundant. I expect people haven't forgotten how to say, empty, or clear?
Hydrated and its related metaphors are essentially marketing tools, invented to differentiate Hibernate from competing products.
At this point Hibernate and other ORM products have used these terms for many years, so Hydrate (and Dehydrate) are here to stay.
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