Now, the calculus of distributive operators is a subject of great extent and importance, but Grassmann's view is the more comprehensive ... . For every quantitative operator may be regarded as a quantity, i.e., as the subject of mathematical operation, but every quantity cannot be regarded as an operator; precisely as in grammar every verb may be taken as substantive, as in the infinitive, while every substantive does not give us a verb. — JW Gibbs, On Multiple Algebra (1866)
... in which we learn that Iverson had antecedents in linguistic parallels, and Gibbs lays some groundwork for Backus' 1977 Turing Award lecture.