One of the mysteries of the English language finally explained.
Definition of APL in English:
APL
noun
ComputingA high-level programming language, typically used for mathematical computations.
Origin
1960s; earliest use found in Proceedings of the AFIPS Conference. Initialism from associative programming language, but now often explained as initialism from A Programming Language, the title of a 1962 book by K. E. Iverson, who devised the mathematical notation which was developed into the programming language.