The modern conception of tenure in US higher education originated with the 1940 Statement of Principles on Academic Freedom and Tenure.

What is the origin of tenure?

early 15c., "holding of a tenement," from Anglo-French and Old French tenure "a tenure, estate in land" (13c.), from Old French tenir "to hold," from Vulgar Latin *tenire, from Latin tenere "to hold" (see tenet). The sense of "condition or fact of holding a status, position, or occupation" is first attested 1590s.

What is tenure and where did it come from?

Tenure was originally created to give teachers academic freedom. It was made to eliminate the fear teachers may have of losing their jobs while they teach and perform duties. Tenure is what makes it very difficult to fire teachers and professors after a certain number of years teaching.