The origins of the term world-building belong to the nineteenth-century, at least according to the Oxford English Dictionary. In fact, the term world-building can be traced, if we are to take the OED at its word, to the 1830s.
Well, some good news. I've been accepted to submit articles/essays to one of the larger Medium publications this morning. Apparently, my article on world-building is getting some serious traction. Can't wait to see what happens.