It's a way of preserving eggs for a year, or two, without refrigeration, by using the mineral lime. The term comes from putting them in glass jars. Chickens usually don't produce as many eggs in winter, and produce an abundance in summer, so this is a great way to balance that out. Or to have spare...

This will help explain it, no affiliation just first link with correct info. https://www.farmhouseonboone.com/water-glassing-eggs/