Comment by jerf

It runs Linux with Windows underneath it, hence Windows is the subsystem being subordinate (in the most literal sense where it simply means "order" with no further implications) to Linux.

Per wongarsu's post, something like the OS/2 Subsystem is an OS/2 system with Windows beneath it, but the OS/2 Subsystem is much smaller and less consequential, thus subsidiary (in the auxiliary sense) to Windows as a whole.

Isn't marketing fun?

This is how we end up with hundreds of products that provide "solutions" to your business problems and "retain customers" and upwards of a dozen other similar phrases they all slather on their frontpages, even though one is a distributed database, one is a metrics analysis system, one handles usage-based billing, one is a consulting service, one is a hosted provider for authentication... so frustrating trying to figure out just what a product is sometimes with naming conventions that make "Windows Subsystem for Linux" look like a paragon of clarity. At least "Linux" was directly referenced and it wasn't Windows Subsystem for Alternate Binary Formats or something.