Why is it called the "standard" deviation? I have a simple - and possibly obviously trivial - question: why is the standard deviation called just that, "standard"? Is it because it standardizes the comparison of data sets and results with respect to their dispersion?
A search on Stack Exchange doesn't turn up this question, nor does a Google search on the etymology of the term yield much of value.
 A: Pearson made up this term in 1894 paper "On the dissection of asymmetrical frequency-curves", here's the pdf. Also, he wrote it with a hyphen, "standard-deviation".
He didn't bother to explain us why he chose the term. Gauss and Airy called it mean error (mittlerer Fehler) and error of mean square. In physics it's usually called "dispersion", btw. 
My guess is that Pearson used the Gaussian (normal) distribution to motivate the usage, so he probably thought that it's "standard" in that sense.
A: I guess that we can have an idea of why a standard deviation is called "standard" by looking at the synonyms of this word (see here). Some of them, like "typical" or "average", make clear the fact that a standard deviation is conceptually a typical or an average deviation to the mean, even if technically speaking you have to take the square root of the averaged squared deviations to the mean of your dataset. In French, we use "écart-type" to refer to standard deviation, "écart" meaning deviation and "type" meaning typical, which probably makes this clearer. I found this a very useful way to provide a conceptual definition of standard deviation to students.
