early 14c., "a thinking beforehand, the act of planning," verbal noun from forethink "think of something beforehand," from Old English foreþencan "to premeditate, consider;" see fore- + think. Meaning "prudence, provident care" is from 1719.
forestall
forester
forestry
foretaste
foretell
forethought
foretime
forever
forewarn
foreword
forfeit