alt Hacker NewsCUA is a union of Mac like mnemonic command keys on Ctrl plus another set (from IBM/Motif perhaps) that use shift+insert,delete etc.
Alt+F4 through Alt+F9 are for Window Menu operations, like minimize, max. etc. Some besides Alt+F4:Close still work on older window managers, I remember SGI supported all of them.
Newer ones tend to hide or even disable the whole menu! Even Windows as it is further lobotomized.
CUA is from IBM and Motif is using CUA.
The shift+insert,delete etc. are from MSDOS as far as I used them – they might have been copied from a previous OS.