Aux
Aux is an abbreviation of auxiliary, used in computing and technology to denote something that supports a primary function, such as auxiliary data, devices, or inputs. The exact meaning is contextual; common uses include auxiliary files, auxiliary power, and auxiliary input or output.
In TeX and LaTeX, the file with the .aux extension is an auxiliary file created during compilation.
In DOS and Windows systems, AUX is a reserved device name that refers to the system console
As a prefix, aux- appears in many terms to denote supplementary components such as auxiliary power, auxiliary