Were these phrases in common usage before Elvis Costello used them in his songs:
“I used to be disgusted, now I try to be amused” from Angels Want to Wear my Red Shoes – 1977. The way he sings it, it sounds like it’s an old, well-known phrase.
“Tragically Hip” from Town Cryer – 1982. This sounds less like a previously existing phrase than the above quote, but since it is such a short phrase people may have been using it before him.
I was under the impression that the phrase “tragically hip” originated in an article or review in Rolling Stone, with reference to the Eagles. I can’t find a reference online, but Don Felder’s book Heaven and Hell: My Life in the Eagles does mention the band’s manager wearing a t-shirt that read “Is Jann Wenner tragically hip?” to a baseball game between the band and the magazine’s editorial staff in 1978.
I am familiar with the song, and I have absolutely no idea what you mean by this. How would someone do that, even if they wanted to? I think this is your imagination. Personally, I cannot recall hearing this sentence anywhere else, except as a quote from this song. Unlike “tragically hip” there is nothing particularly pithy or witty about it. Even if it so happens that someone else, at some earlier time, once put the same words together in the same order, I see absolutely no reason to think that Mr MacManus did not make it up.