China and Japan have just weathered a week of extreme tension, following the Japanese government's decision to purchase the Senkaku/Diaoyu islands from its private owner in a move called "nationalisation"

of the islands. There have been shocking scenes of violent anti-Japanese demonstrations by angry Chinese mobs ransacking Japanese commercial interests in China, causing damage of up to billions of yuan.

Many conflicting theories have been advanced to explain this flaring up of emotion. The Chinese accuse the Japanese of trying to reinforce their control of the disputed islands. The Japanese accuse the Chinese of shamelessly exploiting anti-Japanese sentiment for political ends.

But there is another simple factor at work that might help explain the build-up of emotion: words lost in translation.

As a former official translator in numerous diplomatic negotiations, I've lived through many scenes where translation impeded, not aided, understanding.

And as an ethnic Chinese having lived for a long time in Japan, I am aware of the booby traps for speakers of both the Chinese and Japanese languages, especially given that some words share a similar character in both languages but have in fact acquired quite different tones, and even meanings.

My take on this issue is that there seems to be a treacherous conflict of interpretation of the word "nationalisation" between the two countries. Apparently, the word does not translate into the same meaning on both sides of the East China Sea.

But to explain the difference, a little bit of history is necessary.

There has been, since the 1970s, a discreet and tacit "understanding" between the two countries over the disputed isles, which the Japanese call Senkaku and the Chinese, Diaoyu. Then Chinese leaders Zhou Enlai and Deng Xiaoping proposed "shelving" the dispute for a future solution, to get on with the more urgent normalisation of diplomatic relations between the nations.

For close to 40 years since then, the issue has gone on the backburner - perhaps out of fear of nationalistic reactions at home. Both governments seem to have stuck to this understanding, each side preventing its own citizens from getting close to the islands that, although under effective Japanese administration, became an untouchable no man's land.

When occasional Chinese fishermen were caught venturing into the forbidden area, the Japanese authorities, even during the rule of the very nationalistic Prime Minister Junichiro Koizumi of the Liberal Democratic Party (LDP), promptly and discreetly sent back the fishermen before any nationalistic flame could be ignited on both sides. Meanwhile, Japanese citizens are also forbidden to approach these islands.

This "gentlemen's agreement" was tested with the 2009 change of regime in Japan, when the Democratic Party of Japan (DPJ) took over after nearly 50 years of rule by the LDP. Something was then lost, not in translation, but in transition between the two regimes.

In apparent ignorance of the tacit "understanding" with the Chinese, the new DPJ regime tried, in the notorious 2010 incident of a Chinese trawler ramming a Japanese Coast Guard ship, to fully apply the law and to put the arrested Chinese fisherman on trial, while repeatedly declaring that "there is no such thing as territorial dispute over the Senkaku, which is Japanese territory". Viewed from the Chinese side, this constituted a breach of the "understanding", with the subsequent rise in tension and in emotion.

It did not help that, in April this year, the jingoistic anti-Chinese Governor Shintaro Ishihara of Tokyo started collecting funds from the public to purchase two of the islands from their Japanese private owner (who bought the land from the government some 30 years ago, and has since been leasing it to the national government) with the intention of turning them into a base for Japanese fishermen, in another clear breach of the bilateral "understanding".

That is when the Japanese government, now aware of the danger of such provocation by the Tokyo Governor, hurried to block it by offering to purchase the islands directly, putting them under the state's ownership so that no one would be able to repeat the dangerous provocation of Mr Ishihara.

This is what the Japanese call "nationalisation" of the islands, which was deemed necessary to avoid the eventual ownership of the highly sensitive land by a trouble-making local politician.

In Japan's view, this was merely a "technical" switch from the status of "leasing tenant" to that of state ownership, and should contribute to ensure the continuation of stable administration of the islands under the responsibility of the state. Viewed from this angle, this was a well-meaning act in accord with the bilateral tacit "understanding" on the issue.

Unfortunately, as Japanese Premier Yoshihiko Noda himself admitted, the Japanese government failed to properly grasp what the word "nationalisation" means to the Chinese, and the subsequent emotion it stirs in China.

According to a Japanese blogger living in China, most Chinese he interviewed interpreted this word as a confirmation of "occupation" or "seizure" of "Chinese" land by the Japanese state, and therefore a renewed humiliation for China.

There are of course many other factors behind the violent anti- Japanese riots two weeks ago, including those related to Chinese internal politics and to strategic intents surrounding the islands.

But the failure in translation that led to an abyss in understanding added fuel to simmering tensions.

Nor was this the first time the Sino-Japanese relationship hit a bump over the meaning of a word.

In 1972, when then Japanese Premier Kakuei Tanaka paid a historic first visit to China to cement the reestablishment of diplomatic relations, the negotiations almost broke down over how Japan should repent for the destruction and death its military aggression had caused to China.

The Japanese premier inadvertently angered the Chinese side by declaring at the welcoming state banquet how sorry Japan was for having caused meiwaku, or "deep trouble", to the Chinese people, not knowing that the word in Chinese, "mi huo", means only "confusion" or "bewilderment".

Worse still, it was translated at the time as "ma fan" ("minor bother") to the Chinese audience.

At the end of his visit, Mr Tanaka was received by the ailing Mao Zedong, who offered him a collection of the Verses of Chu (written more than 2000 years ago) in which, the Japanese later found out, there was a line explaining what this fateful word "mi huo" really means.

In the Verses, "mi huo" was used as a term of apology when a person accidentally spilt water on a woman's skirt - a subtle but pointed way of telling Mr Tanaka that his apology lacked weight.

The writer is a retired French diplomat, born in Taiwan and educated in Japan, who worked for 20 years at the French Embassy in Tokyo.