Okidogi is based off of "Okey dokey" and Ferzandipidi is "serendipiti" but other then "monkey" I'm still clueless about the meaning for "Munkidori"
-and yes I know it'll eventually get put in the page but that'll take a while-
Munkidori may be a combination of monkey and hunky dory (slang meaning that things are good). Mashimashira may be a combination of 増し mashi (better, improving) and 猿 mashira (archaic word for monkey or ape).
Seems this is based on a slang too. Hope this helped! Source