腦洞大開 (Simplified: 脑洞大开) seems to be a phrase that's making its rounds in Sinophone online communities (a Google search may be illuminating), although its precise meaning as of yet still eludes me. It seems that different people have been using it to mean very different things. I've observed some using it to mean "thought-provoking", and others to mean essentially "exceedingly foolish".
What I wish to know, however, is if anyone has any idea where the phrase actually comes from. Being a student of mathematics, my obvious idea is the famous exclamation "my brain is open!" by Paul Erdős, the itinerant mathematician who uses the phrase to greet local mathematicians whenever he wanders to a new place. This meaning doesn't really correspond to the usage of the Chinese phrase, but it seems to be a plausible theory of its origin. Could anyone who follows Chinese online communities more closely than I do possibly shed some light on this neologism?