The Hostapedia by
Mark Zilis (2009), "H. 'Hyuga Urajiro' =
H. kikutii leuconata. This
represents a reversal of the
Japanese common name for H. kikutii leuconata, i.e., 'Urajiro Hyuga
Gibōshi'. The plant
itself has green foliage with an intense white underside ("urajiro").
In the last few years, the name 'Hyuga Urajiro' has been used to
market a Japanese import with green and yellow-streaked (white
backed) foliage, but that is not correct."
Mikiko Lockwood in an article on The Hosta Library titled,
A Little About Japanese Hosta Terms defines the term urajiro as white-backed or white underside.