facto pius et sceleratus eodem: :Which leads to (3), the note by Freud on words that can (must?) possess two opposite meanings:
Carl Abel was a German linguist known for his research on Indo-European and Hamito-Semitic lexicology, which was published in his Einleitung in ein Aegyptischsemitisch indoeuropeanisches Wurzelwörterbuch (1886).
It was his theory of the "opposite meanings of primitive words" that interested Freud when, after alluding to the idea in the Interpretation of Dreams (1900a), he wrote an article on the subject ten years later, entitled "The Antithetical Meaning of Primal Words" (1910e). The theory appeared in Abel's article "Über den Gegensinn der Urworte," which appeared inSprachwissenschaftliche Abhandungen, published in Leipzig in 1885.
Basing his thesis on the fact that a Latin word such as sacer signified both "sacred" and "taboo," Abel proposed a theory of the way vocabulary evolves in languages. For Abel, a word in its primitive state can have opposite meanings, which are gradually distinguished through the progress of the rational intellect. "When learning to think about force, we have to separate it from weakness; to conceive of darkness, we must isolate it from light."
For Freud, primitive words mark a stage of symbolization that precedes the separation of opposites brought on by the reality principle. This cultural phenomenon is comparable to the dream process, which enables a representational content to assume a value as the expression of a desire and an antithetical desire. Consequently, the logic of the primary process is felt in a cultural formation as fully developed as language.
See also here. The paper is listed in the Freud bibliography here.