In common usage, NFS is more commonly used as the name of the network filesystem / protocol, like ZFS, XFS, and FAT are the names of local filesystems. They all

In common usage, NFS is more commonly used as the name of the network filesystem / protocol, like ZFS, XFS, and FAT are the names of local filesystems. They all have official expansions, but nobody talks about, say, the "File Allocation Table" filesystem. It is not being used here as an acronym for the general concept of network file systems. It's a specific filesystem/protocol named "NFS", originally the Sun Network Filesystem.