It's a nice headcanon, but I'm afraid that's all it is. For one, Japanese doesn't work the same way English does in regards to written language. It's true that, when reading only the romanized version of the word, it can be pronounced different ways. However, this is not true for the original hiragana. I know Hima's handwriting is not always the easiest to read, but even his "ki" and "chi" look different enough from each other that it's clear which is which. Since Japanese writes the pronounciation of foreign words and not their spelling, it would be written "ki-chi" if that were what he intended. It's not. It clearly says chigi, and is pronounced like chee-gee. That said, I don't know if there is a meaning for it or not, but personally I always just interpreted it as an onomatopoeia for a suppressed frustrated/angry sound Romano makes. Of course, that too could be inaccurate. Only Hima knows.
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For one, Japanese doesn't work the same way English does in regards to written language. It's true that, when reading only the romanized version of the word, it can be pronounced different ways. However, this is not true for the original hiragana. I know Hima's handwriting is not always the easiest to read, but even his "ki" and "chi" look different enough from each other that it's clear which is which. Since Japanese writes the pronounciation of foreign words and not their spelling, it would be written "ki-chi" if that were what he intended. It's not. It clearly says chigi, and is pronounced like chee-gee.
That said, I don't know if there is a meaning for it or not, but personally I always just interpreted it as an onomatopoeia for a suppressed frustrated/angry sound Romano makes. Of course, that too could be inaccurate. Only Hima knows.