think powdered milk. You hydrate it by adding water.

Same idea, only for objects. You hydrate them by adding data.

The term has been used for probably 20+ years.

There's an interesting correspondence with water and data going even further back than that in the English language, think about how often you hear variations on "learning through osmosis" or "hopefully I will pick that up through osmosis". Osmosis is specifically diffusion of water. It's fascinating that so many speakers of English refer to it as "learning through osmosis" rather than the more accurate and less water-centric "diffusive learning".

I've no idea of the etymology for this or why this conflation is surprisingly so deep in contemporary English culture, I've just been fascinated by it for a long time.

This threw me straight back to secondary school, we had a teacher with a fearsome reputation who was berating a class of mine for not revising efficiently, he said "you can't just open your book and learn by osmosis" and some very brave kid piped up with "it's not osmosis sir, that's the movement of water across a membrane. We'd be learning by diffusion, not osmosis". At the very least, this proved we'd been paying attention in biology!

Not sure diffusion is really more accurate than osmosis. It does need to diffuse across the brain membrane, after all ;)

Well, one can assume the eyeballs are akin to an aqueous membrane, but the human ears generally should be non-aqueous for best results. ;)

Over 10 years ago with various ORMs.