I think the similarity to "dosis" is only superficial. I couldn't find any evidence of the name Kappadokia on the LGPN
http://www.lgpn.ox.ac.uk/index.html which covers all Greek names recorded up to the 6th century.
Here are some Greek words that begin with kapp*
http://www.perseus.tufts.edu/cgi-bin/resolveform?lookup=kapp&type=begin&lang=greek&searchText=&options=Sort+Results+Alphabetically&formentry=1&lang=greek
Mike