while its a surprise that an expert doesnt know what a gimble lock lock is, usually, one doesnt ask questions in an interview that can just be looked up. i mean, this isnt a pop quick for developers or something. usually, a measure of expertise would be the projects the person has worked on.
what questions you ask, depends on why you're doing an interview, as well as who (or what) you're doing the interview for. i'd imagine, you'd want to ask questions that your readers would be interested in. you'd want to go a step beyond asking common knoweldge questions, and to something that'd actually require someone in tune with the topic to answer.
rather than ask what the gimbal lock is, ask how the expert deals with it. ask what he'd/she'd suggest to people struggling with it, stuff like that.
just an idea.