 Venn himself did not use the term "Venn diagram" and referred to his invention as "Eulerian Circles".For example, in the opening sentence of his 1880 article Venn writes, "Schemes of diagrammatic representation have been so familiarly introduced into logical treatises during the last century or so, that many readers, even those who have made no professional study of logic, may be supposed to be acquainted with the general nature and object of such devices.Of these schemes one only, viz.