postscriptum
A thing that has been written afterwards; something appended in writing.
rare
Meanwhile, I remain—Ever yours, / Jehu Face. / Postscriptums I hate; but I think you had better / Keep snug to yourself the contents of this letter.
Where it comes from
Learned borrowing from Latin postscriptum, from From post (“after, behind”) + scrīptum (“text, something written”).
Adapted from the Wiktionary entry postscriptum (CC BY-SA 4.0).