I don't know where the "four" came into the name but she probably purchased it from a chain store (expensive) called Tokyu Hands.
http://www.tokyu-hands.co.jp/
The word "riokude" doesn't mean anything in Japanese that I know, and it is not in my dictionaries. The word does not resemble any kind of foreign wood that is written in the Japanese language either.
I will give you what I can on this - 90+ percent of what Tokyu Hands sells (in small pieces) is imported, so most likely it is not a Japanese wood. I do know that they sell zebra wood at times as it does resemble that.
Chris may be able to shed some light on it.
One more thing I will add - For foreign words - Tokyu Hands rarely ever lists the name of the wood from a printed label. Almost always, they take a label and hand write the wood species on it - often making it difficult to get accurate. If a person (the buyer) does not know of the wood species by name or sight, it is often difficult to determine strictly by the hand written name on the label. Shucks, I have asked sales persons before and they couldn't pronounce some of the names. :wink: