I don't know the answer to this one Pak Ganja. I have a gut feeling that the name might be tied into the finding of the keris under a stupa at Borobudur.
I never heard this name used in Jawa in the late 1960's and the 1970"s.
Here's a link to some of my "iron ancestors" (intended reference to the upcoming publication.)
http://www.kerisattosanaji.com/kerissajen.html