Q. If I use a term in writing such as “infra dig,” should I use quotations with parentheses to explain the term immediately following the expression? I assume I should, as “infra dig” is a seldom-used term. Most authors seem (to me) to just include their arcane words and phrases to force the readers to look up the words or not, as they choose.
A. Try to be sensitive to your intended readers. To gloss “infra dig” would insult the intelligence of some audiences; other times, readers might need a little help. Sometimes a writer needs to use a particular expression. You might have to say “infra dig” because you’re writing an article about expressions that derive from Latin. In those cases, it’s appropriate to gloss if you are trying to teach something or reach a wide audience.
As for your authors’ motives, it’s not necessarily perverse for a writer to leave difficult words unexplained. Skilled writers convey the meaning through the context. Skilled readers keep a dictionary at hand. If a word is perfect for a given context and it would break the mood to explain it, a writer just has to trust that any reader who cares will figure it out.
Oops—I forgot to answer your question! Yes, for introducing arcane expressions, quotation marks with a parenthetical explanation work well.