This four character idiom essentially means "frivolous and thoughtless". This word was used in reference to English words (and words from other Western languages) in a time the Japanese Empire was in war with these nations, particularly starting in 1940. With this word in mind, it fueled the boycott movement of these words for their 敵性 (inimical character).

From a point of law, there was no rule put in place by the government labeling words of foreign origin as either "軽佻浮薄" and "敵性", and from a practical level, the nation still possessed relations with certain nations and the language had been borrowing words from Indo-European languages since the 1950s. Thus, a reversal of centuries of borrowing (although generally light up until the Meiji Restoration), would essentially be possible as any changes in the lexicon of the language would be most effectively implemented in primary education to the younger population.

The movement was a natural reaction to the war. So, it didn't have a strong effect. So, in fields such as science, essentially no changes terminology were made. As simple English words as well as 和製英語 had been used before and during the war in not just the media but also by general citizens, it would, again, have been impossible anyway for the effect of English to be fully eliminated. As examples of words that were even used in government publications, シャツ, コンビネーション, チョッキ (from Portuguese meaning vest) never stopped being used.

In fact, although there were attempts by the Ministry of Education to rid of English education in schooling, due to English's role as the lingua franca of the world, it was ultimately left as an optional course of study. That is not to say that some schools went ahead and banned it as an enemy language, but it is not the case that English education or the use of English words--whether when speaking English or Japanese--was ever implemented.

However, there were a few things that were put in place that did influence the use of language in schooling. For instance, "pro-American" phrases were replaced, the use of Western-style dates was made limited*, and phrases felt to be derogatory to Japan were taken out of texts.

As for the second point marked with an asterisk, this has made a lasting impact on Japan. Though the Japanese-style of telling the date has never ceased and has been the most used throughout Japanese history, it is fair to say that before war tensions escalated that the Western calendar as well as customs on telling the date was becoming more and more common. Nowadays, the two systems balance out by being used in specific situations.

This sort of bifurcation is not natural for when one system is quickly replacing an older and more antiquated system. If we relate this to the use of Sino-Japanese and native numbers, we see that the newer Sino-Japanese numbers have been slowly replacing native numbers. So, if customs in using the Western and Japanese calendar were explicitly established in educational texts before the newer system fully took over, then these new conventions would take hold.

It was also not the case that loanwords were banned in military use. For instance, although we will look at baseball terminology later in this lesson, ストライク was still used throughout the war in war related materials when speaking of baseball. The French word スペリー for "searchlight" and ピスト for "cockpit" were very important words at the time.