Latin factum, thing done, from facere (to make, do). Early English fact meant an act, a crime ('after the fact'), an accomplishment; the sense of verified truth is 16th-17th century, rising with law courts and the Royal Society. Facere's family is colossal: factory, fashion, feature, difficult, benefit, artificial.
The eternal complaint, refreshed every generation: facts are supposed to be settled, yet every era's facts come with an expiration date. The word's history feeds the cynicism, if facts are made (facere), they can be made otherwise.
The philosophical nerve: fact encodes the radical claim that truth is a species of manufacture. Constructivists quote the etymology like scripture; realists point out that a deed done is stubbornly unchangeable, the fact as the one thing even power cannot unmake. The word holds both charges.
When did done become true, and who performed the conversion?