The phrase "first attached" is correct and usable in written English.
For example, you can use it to say: "The first attached document contains all the relevant information for this task."
He was first attached to the Royal Scots regiment.
Bratt Pitt was first attached to play Fawcett in Gray's film.
Can we trace it back to its origin, the point when it was first "attached?" Is Gerhartsreiter a real Rockefeller?
Director DJ Caruso (Eagle Eye, Disturbia) was at first attached to the project, with his frequent collaborator Shia LeBeouf rumored to be circling the lead role of Brown.
There was one striking omission in this me-too diatribe, however: the "Feminazi" label, first attached to Proudman by Vine and then used of her on the paper's front page and repeatedly inside, was nowhere to be seen.
In a series of experiments, Seligman and Maier first attached dogs to a harness, a kind of rubberized cloth hammock, with holes for the dogs' legs to dangle free.
First, attach the vacuum attachments supplied by the manufacturer.
But ticks must first attach to the skin of their hosts and attachment must be effective for the duration of the tick's blood meal.
First, attach Mr. Perry to Mr. Giuliani.
"Mr. Hubbard will first attach hooks to his eyelids," the master of ceremonies called out.
Ms. Sweesy first attaches a pull-ribbon to the length of a bottle, and then encloses the bottle in shrink-wrap, leaving the top of the ribbon exposed.
