what are some phrases that you use in your hobby or work that would make no sense to outsiders?

Computers are an endless source of these. Someone else already mentioned daemons and killing orphans; I submit "I only ever ssh into that box, so I keep it headless." ("I only ever access that computer via the terminal, so I don't install any software that uses graphics.")

Conlanging (constructing languages) inherits all the jargon of linguistics, and then adds a bunch of slang on top for good measure. "I was worried that glomming tense markers to subjects in my analytic clong was unnaturalistic, but it turns out ANADEW" is the kind of thing I might say in a casual conversation with another conlanger.