Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.

Ex Input:
I've found that expression on a website, and I don't understand it. At first I thought it was because the canary is yellow and the coal black... but it doesn't make much sense.

Ex Output:
A canary in a coal mine is an advanced warning of some danger. The metaphor originates from the times when miners used to carry caged canaries while at work; if there was any methane or carbon monoxide in the mine, the canary would die before the levels of the gas reached those hazardous to humans. See here.

Ex Input:
Is there a name for these kind of doubled words? For example: hanky-panky flim-flam hoity-toity boo-hoo zig-zag Note that some rhyme and others do not.

Ex Output:
hanky-panky is an example of rhyming reduplication zig-zag is an example of ablaut reduplication.

Ex Input:
This came up recently on programmers.SE, when someone (a Russian, presumably non-native English speaker) asked why we used the term 'sister sites', instead of 'brother sites'. Of course, I'm a native English speaker, and I have no idea either, hence this question. The full question, for context, was 'Several of our sister sites have taken to featuring Questions [...]'. It does seem odd, considering that English (usually) uses masculine terms as the default.

Ex Output:
I suspect the terminology sister sites is derived from sister cities. Traditionally, cities, countries, and ships have been personified as feminine in English, although this is growing less common due to the influence of women's rights.