This is a non-sequitur. Japanese/Chinese have no relationship to Indo-European or Germanic languages, thus this has nothing to do with fuck. If you were to go through the worlds languages you would likely find thousands of examples of words that were similar to each other in sound but completely different in meaning. And just as likely, you'd find examples of words that, through the magic of chance, happened to have the same meaning and similar sound. For example, in Japanese, children have called their mothers "mama" since long before the first westerners came to Japan. This example is a little different because it's hypothesized "mama" is commonly a reference to "mother" for children because the mouth movements are similar to those of a suckling baby. But the point is, languages with no historical connection should not be construed to be related because there are words with similar sounds or with similar sounds and meanings.
Sorry, for the sidetracked post.... Fuck.