Soft Brick => You can build the house with a lot of them, but when the wolf huffs and puffs, it will fall.

Hard Brick => The house you build, will not be breakable by the wolf’s huffing and puffing.

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Would you build a house out of a metaphorical term? It’s not literal. If a phone doesn’t boot it’s as useful as a brick until you fix it.

The term exists, and has been used in rooting circles since at least 2012 that I know of, since that was when I rooted my first device and ran across the term.

While it certainly doesn’t make much sense as a term, that’s different from the term not existing.