Comment by adrian_b

The concept of extended file attributes has been introduced by HPFS, in OS/2, in 1989.

From HPFS it was taken by SGI XFS (the ancestor of Linux XFS) and MS NTFS, both in 1993.

From there it has spread to various other file systems and specifications.

The concept of resource forks is earlier, but both are examples of using alternate data streams in a file.