Ask anyone over age 50 if they ever heard the word “Chanukah” when they were growing up. The odds are that they didn’t. It was called “Hanukkah” back then. Why is it often called “Chanukah” today? It’s hard to say, but here’s one guess: the Jews know that “Chanukah” looks and sounds closer to “Christmas” than “Hanukkah.” That makes Hanukkah, and the Jews, seem a little less “alien” to gentiles. (The term “Judeo-Christian,” rarely heard before World War II, works the same way) [1]:
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[1] Jews excuse the recent change by saying that “Chanukah” is similar to how “Hanukkah” sounds when spoken in Hebrew

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