1530s, "action, anything done," especially "evil deed," from Latin factum "an event, occurrence, deed, achievement," in Medieval Latin also "state, condition, circumstance," literally "thing done" (source also of Old French fait, Spanish hecho, Italian fatto), noun use of neuter of factus, past participle of facere "to do" (from PIE root *dhe- "to set, put"). Main modern sense of "thing known to be true" is from 1630s, from notion of "something that has actually occurred."

Compare feat, which is an earlier adoption of the same word via French. Facts "real state of things (as distinguished from a statement of belief)" is from 1630s. In fact "in reality" is from 1707. Facts of life "harsh realities" is from 1854; euphemistic sense of "human sexual functions" first recorded 1913. Alliterative pairing of facts and figures is from 1727.

Facts and Figures are the most stubborn Evidences; they neither yield to the most persuasive Eloquence, nor bend to the most imperious Authority. [Abel Boyer, "The Political State of Great Britain," 1727]

c. 1500, from Middle French faction (14c.) and directly from Latin factionem (nominative factio) "political party, class of persons," literally "a making or doing," noun of action from past participle stem of facere "to do" (from PIE root *dhe- "to set, put"). In ancient Rome, originally "one of the four teams of contenders for the chariot races in the circus," distinguished by the color of their dress. Later "oligarchy, usurping faction, party seeking by irregular means to bring about a change in government."

A spirit of faction, which is apt to mingle its poison in the deliberations of all bodies of men, will often hurry the persons of whom they are composed into improprieties and excesses for which they would blush in a private capacity. [Hamilton, "The Federalist," No. 15]

1973, "published statement taken to be a fact because of its appearance in print," from fact + -oid, first explained, if not coined, by Norman Mailer.

Factoids ... that is, facts which have no existence before appearing in a magazine or newspaper, creations which are not so much lies as a product to manipulate emotion in the Silent Majority. [Mailer, "Marilyn," 1973]

By 1988 it was being used in the sense of "small, isolated bit of true factual information."