According to Dictionary.com
forecast[fawr-kast, -kahst, fohr-]
verb (used with object), forecast or forecasted, forecasting.
to predict (a future condition or occurrence); calculate in advance
to forecast a heavy snowfall; to forecast lower interest rates.
to serve as a prediction of; foreshadow.
to contrive or plan beforehand; prearrange.
verb (used without object), forecast or forecasted, forecasting.
4.to conjecture beforehand; make a prediction.
5.to plan or arrange beforehand.
noun6.a prediction, especially as to the weather.
7.a conjecture as to something in the future.
8.the act, practice, or faculty of forecasting.
9.Archaic. foresight in planning.
According to Online Etymology dictionary, fore- has an etymology of Middle-English but Cast doesn't have a known origin. Forecast doesn't have a known origin either.
So what is the origin of the word forecast?
Best Answer
Etymonline derives forecast from two English words, fore- and cast.
Fore- is derived by the American Heritage Dictionary of Indo-European Roots from the conjecturally reconstructed PIE per,
via conjecturally reconstructed Germanic, *fura, before.
Etymonline identifies cast as cognate with Swedish kasta, Danish kaste, North Frisian kastin, "of uncertain origin". OED 1 provides a few more apparent cognates from North Germanic and invites comparison with
Wiktionary offers a conjecturally reconstructed verb from Proto-Germanic:
AHDIER does not index cast, and the online database to Pokorny appears to offer no term from which cast is derived, suggesting that no one has convincingly pushed the origin of cast farther back than common Germanic.