Question of the Day #67

"My rule of thumb when out drinking is never to mix different kinds of drinks."

上記の文で、rule of thumbの意味は？
In the sentence above, what does "rule of thumb" mean?

答えは、コメントに書いてください。
Write your answer in the Comments.

明日、ここに答えを書きます。
I will add the answer and other remarks here tomorrow.

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解答

意味： 英辞郎によると、


1. 〔よく使う〕おおまかなやり方◆正確ではないが実用になる方法を指す。
2. 経験則

Answer

According to The Free Dictionary:

A useful principle having wide application but not intended to be strictly accurate or reliable in every situation.

Etymology/語源

英辞郎によると、

【語源】きこりが長さを測るのに、親指を使ったことからと考えられている。しかし、妻を殴るのに許容されていた板の厚さが、親指の太さまでであったからという説もある。

とあるが、The Phrase Finderでは、この語源はいずれも否定されている。このイディオムは1600年代から使われているが、語源は定かではないとしている。

According to The Phrase Finder:

The phrase itself has been in circulation since the 1600s. The earliest known use of it in print appears in a sermon given by the English puritan James Durham and printed in Heaven Upon Earth, 1685

"many profest Christians are like to foolish builders, who build by guess, and by rule of thumb, (as we use to speak) and not by Square and Rule."

The origin of the phrase remains unknown.

The entire article is much longer and involves an unsubstantiated story concerning English law, so if you have time on your hands, you might find it interesting.

Examples

• A good rule of thumb is to plant your seedlings around the end of　May.
• Going by a rule of thumb, we stop for gas every 200 miles when we are traveling.
• His work with the youth group is largely by rule of thumb.