Or at least change the spelling to accomplish the same goal. Whats wrong with Oomami or Umaami to make it easily identifiable on the web?
[1] - https://github.com/qarmin/czkawka [2] - https://github.com/qarmin/szyszka [3] - https://github.com/kopia/kopia
That's all what I can remember. I wouldn't count KDE apps that do sound Polish or Slavic just because they "had" to replace initial letter with K to keep the leading theme.
Then people behind MATE desktop on the other hand named apps in their project using Spanish words, e.g. file manager Caja - "box" or "case", documents reader Atril - "lectern" or "music stand"
As for Japanese words usage, it's still the outcome of anime&manga wave that bloomed in the end of 90s. What I find surprising is that nothing comparable happen when k-pop and k-dramas rise to popularity - there's a significant fascination of South Korean culture but not as intensive that would show interest in using vocabulary in the West as that happens with Japan. Perhaps mukbang, "eating broadcast" is the only exception.
By the way I have a single Japanese word named project, but it's related to the language, and that name has two other connections with the project content.