The story
Coined by English mathematician, biometrician, and eugenicist Karl Pearson in 1894 in his paper "On the dissection of asymmetrical frequency curves".
Etymology from Wiktionary, CC BY-SA 4.0.
standard deviation
Today it means: A measure of how spread out data values are around the mean, defined as the square root of the variance. Represented with the Greek letter σ (sigma). Full definition →