Refrigerator drips water inside
Warm moist air goes into the fridge and condenses. This is where you get the moisture. Normally, there's a drain, perhaps below the veggie drawers, that ducts the excess moisture away to a tray below the evaporator coils. 

It's common to have this drain clog. You can try pouring in boiling water to clear it, but you may overflow the bottom tray and need a mop.

You can also try soft copper wire, like 14 gauge stripped electrical wire, which should not poke any holes in anything yet still be stiff enough to clear the jam.