I had heard of the band Fugazi, but I didn't know their name derived from a Vietnam acronym: "Fucked Up, Got Ambushed, Zipped In."
Originally, the term derived from the word "fugacious," which Wikipedia defines as meaning "ready to flee" (Run away!) (I suppose that means Lela Dowling's Weasel Patrol, whose motto was "Protect, serve, run away," was fugacious), but MW11 defines as a synonym for "evanescent."Which brings us to the nominal topic of this entry: "fugacity," which is "a measure of the escaping tendency of a substance," especially a vapor.
So I suppose that things that are easily lost or very slippery could be said, metaphorically, to have a high fugacity.
I have no idea at this point where I ran into this word. It was only after I looked it up that I started wondering about the Fugazi connection.