Adding on to what glowacks said, when the Japanese adopted the Chinese characters, they assigned their own words to the characters sometimes, and preserved the Chinese pronunciation sometimes. More often, they use the traditional Japanese word for single character words, and intermix between traditionally Japanese and traditionally Chinese words when they use multi-character words.
So the word “kujira” will have predated the Chinese character and won’t have influenced the design of the Chinese character. But, since the Japanese don’t have a writing system before adopting the Chinese one, there’s no way to track the history of the orally-transmitted word, kujira.
On the Chinese side, if “whale” was added to the lexicon sometime later, you could possibly find some etymological history to it more interesting than just “capital whale”, in how the pictographs morphed over time, but that won’t tell you anything about kujira.