Why is the ninth month called September?
1874, a back-formation from extrapolation by analogy of interpolate. Said in early references to be an expression of Sir George Airy (1801-1892), English mathematician and astronomer. Related: Extrapolated; extrapolating.
A mathematical procedure designed to enable one to estimate unknown values of a parameter from known values. A common method of extrapolation is to look at data on a curve, then extend the curve into regions for which there is no data. Extrapolation is often used to predict the future.