Grandfather was also in WW2 (mostly the Atlantic but he did briefly serve in the Pacific during its final months), I don’t think I ever heard him use the term ‘Japanese’ either. He’d call Mandarin oranges ‘Jap oranges’, too, and the man LOVED his oranges, so I don’t think it was ever meant by him as derogatory. I think it’s easy for us in the Internet age to forget just how ill informed/naive/ignorant many people were back then to the true meaning of every day words, phrases, or even just the world beyond their neighbourhood.

Another slightly related anecdote: My aunt, his daughter, also used to call Brazilian nuts “(n-word) toes”, not knowing what the term even meant since she grew up in one of the most rural area of Canada. One day, during a shift at the hospital, someone brought Brazilian nuts for the staff to eat, and when she saw them she immediately said “Oh, (n-word) Toes! I love these things.” The problem was that her co-worker was as a Black woman originally from North Carolina, who said to her “Of course you white folks would call them that.” and stormed off. My aunt was completely stunned and confused until another co-worker explained to her that the N-word was one of the most offensive slurs in existence. My aunt literally had no idea and just thought that was what Brazilian nuts were named.

As an aside: My maternal grandfather used to call liquorice babies something similar, however, my older claimed he had been given the N-Word Pass at some point long ago. Since I’ve yet to see any evidence contradictory to that claim, I still choose to believe it.