Here is a list of commonly used abbreviations:

DRY = Don’t Repeat Yourself. With this is ment that you shouldn’t repeat the same code in many places throughout the codebase. Having the same code repeated in many places makes the code harder to maintain because changing the behavior of your program means that  many changes have to be made, in many different locations. Duplicated code also makes it more difficult to resolve bugs because all duplicates have to be found and the bug solved in each code snippet.

ODR = One Definition Rule. This states that any translated unit must not have more than one definition of a method or class. That is to say that you must not have two functions or classes with the same name in the same namespace in one program.  

TU = Translation Unit.