  Proof-theoretic semantics has several roots, the most specific one being Gentzen’s remarks that the introduction rules in his calculus of natural deduction define the meanings of logical constants, while the elimination rules can be obtained as a consequence of this definition (see section  2.2.1).  More broadly, it belongs to what Prawitz called general proof theory (see section  1.1).  Even more broadly, it is part of the tradition according to which the meaning of a term should be explained by reference to the way it is used in our language.