Pith: from the Old English word piþa, meaning substance or the essence of something.
My husband has been craving fresh lime infused water, of late. Mind you, this beverage does not only differ in that you use small green limes instead of yellow lemons. Instead of halving your citrus fruit and squeezing out the juice, you quarter them and throw the peel, pith, and membrane into the blender with your water. Immediately after blending your concoction, you must strain it. Add sugar to taste.
Result: foamy liquid with slightly more bitter than sour flavor that you get with lemonade.
Note: Someone suggested that a pinch of salt helps combat the bitterness. I haven’t tested the claim.
Opinion: I prefer saving the zest for other culinary adventures over having it flavor my limeade.