c.1303,
gessen "to estimate, appraise," originally "take aim," probably from Scand. (cf. Middle Danish
gitse, getze "to guess," O.N.
geta "guess, get"), possibly infl. by M.Du.
gessen, M.L.G.
gissen "to guess," all from P.Gmc.
*getiskanan "to get" (see
move). Sense evolution is from "to get," to "to take aim at," to "to estimate." U.S. sense of "calculate, recon" is true to the oldest Eng. meaning. Spelling with
gu- is late 16c., sometimes attributed to Caxton and his early experience as a printer in Bruges.
Guesswork is from 1725.
Guesstimate is 1934, coined by statisticians, blending
guess and
estimate.