The term "Fenestration" is derived from the word "Fenestra" and Fenestra is the Latin meaning of "Window".
The word fenestra has been used in the building industry by architects, builders, engineers, and glaizers for many years when they're referencing the windows and doors of the building envelope of a commercial construction project. After so many years of using the term fenestra the building industry now refers to fenestra as fenestration.
The relationship between the word Fenestration too windows and doors is the fenestration is a testing organization the tests the quality and strength of any given product. In most cases they make sure that any given building product can meet or exceed local code requirements for any given region.
Example of Fenestrations Testing
Would be for the aluminum storefront industry and their storefront doors & windows that are installed along a coastal region where there is a high probability of hurricanes. These types of coastal regions need special types of storefront doors that have been tested by the fenestration. These storefront doors are referred to as "Impact Storefront Doors" and are missile resistant doors; moreover, the fenestration is referring to missile as the debris items flying off the ground into any given building industry product, like storefront doors and windows.