These pairs are not necessarily Orwellian-like, as they don't seem to be used to obscure or distort meaning in a way that's characteristic of Orwellian language. The use of euphemism in the context may be intended as a strategy of tactfulness rather than an attempt to obfuscate meaning. "The rat but a tradition now" suggests that something that has become outdated or obsolete. It reminds me of some of Poe's themes on obsolescence. The specific literary device used by Dickinson is often referred to as "indirect expression." Her discourses can be intriguing and complex. Now, I feel like a Sesquipedalian on a basic English language learning site.

"Reputed" just means "assumed to be true (but possibly not)". Ned's behavior was said to be an indiscretion, but calling it a "reputed" one introduces some doubt. In the little poem written by Emily, I believe the cat to be Emily herself. Emily is old now, at least in comparison to her nephew (or grand-nephew) Ned. That's why her "martial time" is "forgot". That's why chasing rats, to her, is a mere "tradition" in the sense of being something remembered (and never forgot). I suppose that the actual tradition is that of thinking about rats. Since Ned has been mischievious, he is the "rat". "Rat" is not used in a nasty way, just playfully. In saying that this old cat no longer has the desire to catch the rat, she is merely saying that she is inclined to overlook Ned's "reputed indescretions". Emily does not want to scold him.