Barbara Liskov, winner of the Association for Computing Machinery's A.M. Turing Award, discusses the origins, and naming, of the Liskov Substitution Principle which defines the relationship between subtypes and supertypes in object-oriented programming. This clip taken from an interview conducted with Liskov by Tom van Vleck for the ACM on April 20, 2016. Video of the full interview is available as part of Liskov’s ACM profile at https://amturing.acm.org/interviews/liskov_1108679.cfm.