I planted Soapwort (Saponaria officinalis) in the garden for its spreading, sprawling quality. It weaves in and out of other plants- "Bouncing Bett" is an old nickname for it. 

 As I've noted before the word "wort" in the common name and "officinalis" in the Latin name indicates that a plant once had a real or imagined practical use. Soapwort is indeed a practical plant. The leaves contain saponins and lather up to make a gentle detergent. It was probably introduced to the UK in medieval times for that purpose by the wool and cloth trades.