What does Lather (in the sense of bath time) mean?
"Lather" in the context of bath time means to make lots of soapy bubbles and foam. When you put soap on a sponge or your hands and rub it on your body, it creates these frothy bubbles, and that's called lathering up. It's like making a fluffy, soapy cloud on your skin to help clean it and make it smell nice.