Whether you’re looking to sell or buy a home, you will no doubt encounter the multiple listing service, or MLS. The site and service are, in many ways, the very lifeblood of the real estate business.

Yes, the MLS seems like an invention of the modern age. But, in fact, the term “multiple listing”—and the overarching concept behind it—was first coined in 1907. Back then it described the old-timey ...