Probably discovered by accident, since if you harvest honey combs before they're capped there is still a high percentage of water in the nectar. If you store this for awhile it naturally ferments and makes a very sweet mead. I've done it myself by accident.
I do it on purpose. Just bottled 5 gallons last Saturday. Should be fit to drink in a couple of months. Although a good long 6-8 month rest is better.