As others have mentioned, it comes up in information theory, or maybe in some subfields of combinatorics and probability. I learned it tangentially in various p

As others have mentioned, it comes up in information theory, or maybe in some subfields of combinatorics and probability. I learned it tangentially in various parts of physics. But I might just recommend going to the source! which is Claude Shannon's seminal masters thesis on coding: http://affect-reason-utility.com/1301/4/shannon1948.pdf http://affect-reason-utility.com/1301/4/shannon1948.pdf . It's surprisingly readable and worth at least skimming if you like this stuff.