According to The Hostapedia by Mark Zilis (2009), "H. 'Iwa G' = H. longipes 'Iwa Soules'...Normally "Iwa G" would just be short for "Iwa Gibōshi", the Japanese common name for H. longipes. In this case, however, Van Wade of Wade and Gatton Nursery (Closed 2019) of Ohio credits this plant to "Soules", i.e. Marge Soules. Marge imported a form of H. longipes from Japan, which was dubbed 'Iwa Soules' by Schmid (1991)."

Mikiko Lockwood in an article on The Hosta Library titled, A Little About Japanese Hosta Terms defines the term iwa as rock, Iwa Gibōshi or H. longipes.