Archaic legal term for a person who has been subject to attainder, or historically, a person who achieves or obtains something.
From 'attain' plus the agent suffix '-er,' creating a noun for someone who attains or achieves. In legal terminology, it specifically meant someone upon whom attainder had been imposed.
The word 'attainer' is almost extinct in modern English, living on mainly in historical legal documents and genealogical records where it appears beside the names of ancestors stripped of property and rights by medieval courts.
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