The story
See birth-to-potty nappy.
Etymology from Wiktionary, CC BY-SA 4.0.
birth-to-potty diaper
Today it means: Synonym of one-size diaper (“a type of cloth diaper which can be adjusted and lengthened to match the baby's growth, thus allowing the diaper to be worn from around birth (by a newborn) to potty-training age”). Full definition →