Why are wisdom teeth called 親知らず in Japanese?


Why are wisdom teeth called 親知{おやし}らず in Japanese?

The literal meaning seems to be something like "unknown to the parents".




From [the wikipedia
article](http://ja.wikipedia.org/wiki/%E8%A6%AA%E7%9F%A5%E3%82%89%E3%81%9A):

>
> 赤ん坊の歯の生え始めと違い、多くの場合親元を離れてから生え始めるため、親が歯の生え始めを知ることはない。そのため親知らずという名が付いた。また、乳歯が永久歯の「親」と考えると、親知らずには、対応する乳歯が存在しないので、「対応する乳歯が無い＝親知らず」として命名された、という説もある。

Translation (please edit where appropriate):

> In contrast to baby teeth, wisdom teeth often start to grow in after you
> become independent of your parents. Therefore, your parents do not know
> about them. This is the reason they are called 親知らず. Also, if you think of
> baby teeth as the "parents" of permanent teeth, 親知らず do not have
> corresponding baby teeth, as a result, some people claim that 親知らず means
> teeth which do not have corresponding baby teeth.




From [the wikipedia
article](http://ja.wikipedia.org/wiki/%E8%A6%AA%E7%9F%A5%E3%82%89%E3%81%9A):

>
> 赤ん坊の歯の生え始めと違い、多くの場合親元を離れてから生え始めるため、親が歯の生え始めを知ることはない。そのため親知らずという名が付いた。また、乳歯が永久歯の「親」と考えると、親知らずには、対応する乳歯が存在しないので、「対応する乳歯が無い＝親知らず」として命名された、という説もある。

Translation (please edit where appropriate):

> In contrast to baby teeth, wisdom teeth often start to grow in after you
> become independent of your parents. Therefore, your parents do not know
> about them. This is the reason they are called 親知らず. Also, if you think of
> baby teeth as the "parents" of permanent teeth, 親知らず do not have
> corresponding baby teeth, as a result, some people claim that 親知らず means
> teeth which do not have corresponding baby teeth.

