Guess Ishiyumi-sensei needs some way to justify her skimpy clothes.

...Though "kunoichi" by itself is probably already a good enough justification.

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Anyway, by convention (in fiction) ninja characters are usually given highly meaningful names. Usually there's one or two (or maybe three) parts of the name that alludes to a meteorological event (wind, rain, snow, etc.), environmental phenomena (plants, usually), astrological bodies (almost always the moon, and sometimes a specific lunar cucle); plus one other part that alludes to stealth or a state of hidden (the -zou ending part meaning "storehouse" or "hiddenness" is very common on 'personal' names for this reason. More for male ninjas though, it's rarer for kunoichi. Also "moon", as mentioned earlier, which itself also alludes to "being hidden" Like the back side of the moon). So both of Shinzou's names have these elements, plus the word "heart" to allude to her role as the heart of Kagerou.

(Names alluding to animals are also common, but fictional ninjas having those kind of names usually employ some kind of martial art that is inspired by their namesake animal.)