First of all let me say that this question was a stumper. None of the native speakers I know knew the answer. So I went to http://www.google.co.jp and put in a search for GOMI and KATAKANA. I did the search by typing them both in KATAKANA with a space between them.
There were close to 9,000 results so I started to sift through them. It is amazing how many page have both those words on the page but have nothing to do with why GOMI is written in KATAKANA.
I did find a few things prior to finding the actual answer that I would like to share because I thought it was interesting.
First there was this sentence that I found that was one person's opinion about GOMI being written in KATAKANA.
This sentence at first I thought was the answer. The sentence says that perhaps the reason that the GOMI in GOMIBAKO is written in KATAKANA is a "meaningless uneccessary sense of pride". I thought that this sentence was really cool because it implied that Japan wants to think of GOMI as something NOT of Japanese origin.
I also came upon this little gem that I think is important for anyone studying Japanese to know.
This sentence means, "The world is overflowing with katakana letters and I don't know what they mean". This sentence is great because it shows that even some Japanese people are upset with Katakana. I had heard of a debate a while back to abolish KATAKANA and use ROMAJI in it's place but it never got much support apparantly.
And finally the answer! The answer is the GOMI should NOT be written in KATAKANA. It is a Japanese word so therefore should be written in HIRAGANA (there is no KANJI for it). I found this answer by reading a scathing letter sent to a writter of a Japanese magazine. The writer had written GOMI in KATAKANA as many people do. Heck even when you type it into the computer the first thing that comes up is the KATAKANA version!
The letter went on to say that GOMI is never written in KATAKANA in the newspaper and furthermore that any politician who writes GOMI in KATAKANA when discussing Japan's
gomi mondaitrash problem would certainly be considered uneducated about the trash problem by people in the trash administration.
The letter even goes as far to say that some people consider the word GOMI in KATAKANA a discriminatory word. What they mean by that is that because KATAKANA is boxy and simple it stands out and therefore is used many times to show shocking things. If you pay attention you will see TV shows and magazines use KATAKANA to represent Japanese words when they want to catch your eye.
In the end, the author apologizes and promises to write GOMI in HIRAGANA.
The continuing trend towards KATAKANA Even though it might not be correct to write GOMI in KATAKANA it is important to remember that the many of Japanese people DO! If you don't believe me just put GOMI in KATAKANA into a search on http://www.google.co.jp and see for yourself. Another word that is written in KATAKANA all the time now is KEITAI which is short for
keitaidenwa, which means cell phone. KEITAI is obviously much easier to write in KATAKANA than KANJI. You never know in 10 years maybe it will be made official that GOMI and KEITAI be written in KATAKANA.
This was so interesting to read! I now know you put real effort into answering all of the questions posted on your site. The person who wrote this question must be an observant person. I think this is a very note worthy cultural tid bit.
I too noticed that katakana is used in advertising a lot. But we do the same thing in America, it's just a grammatical difference: Got milk? instead of "Need milk?" or Apple's "Think Different" instead of "Think Differently". Or spelling differences like I sign I saw recently for a restaurant "Kozy Korner Kafe". Can you imagine a Japanese person trying to learn English and seeing this one! Dan
'Gomi' o kakukoto ゴミ does have a kanji 「塵」 but I think it is rarely, if ever used. Maybe just in dictionaries. It's also read as ちり (dust) which is also usually just written in hiragana I think.
Some of these old questions are really great. I remember wondering why ゴミwas so often written in katakana myself, since it is a native Japanese word. Even in formal material like textbooks, I'd see it written this way.
My theory is that since katakana is often used for emphasis or as an eye-catching mechanism (like on signs, advertisements, etc.), it seems likely and appropriate that one would commonly see signs on public trash cans and such written ゴミ箱 . Over time, it's probably become the commonly accepted way of writing it.
The idea that katakana is used because Japanese would rather not associate the word ごみ with native Japanese language sounds like creative speculation to me.
hmm Well I guess like imported words from European countries and America are written in Katakana..I guess from China they are too. The kanji Kinzokusei no Inu mentioned may of came from the chinese character "chen" "塵" meaning dust too. Even though the pronounciation is different, the kanji is the same and so when not using the kanji it is treated as a foreign word..in katakana. Umm, not sure if any of that made sense but I may as well post..lol
The kanji I mentioned is that character, and in Japanese, its "on-yomi" (Chinese reading) is "chin" or "jin". It doesn't have any relation to the usage of katakana for "gomi" however. I actually just posted that as kind of a trivia thing. There are many Japanese words that, though there is a way of writing them in kanji, are more commonly written without. For words like this, it is usually better just to write the common phonetic spelling, as even a native Japanese will probably not know them.
I like George's "Beware of dictionaries" warnings. This is so true.