The story
The concept and the term are ancient; Athens’ democratic ideology of free speech (παρρησία (parrhēsía)) is thought to have emerged in the 5th or 6th century B.C.E. The first occurrence of the phrase freedom of speech recorded by the Oxford English Dictionary dates to 1567, and it also appears in the English Bill of Rights, among other works: see the quotations.
Etymology from Wiktionary, CC BY-SA 4.0.