1835, "structure enclosing a large wheel," especially one over the steering wheel of a steamboat, thus "pilot house;" from wheel (n.) + house (n.). Baseball slang sense of "a hitter's power zone" attested by 1990.
Slang definitions & phrases for wheelhouse
wheelhouse
noun
A batter's preferred hitting zone over the plate; kitchen
[1959+ Baseball; probably fr the controlling prominence of the wheelhouse on a riverboat or a ship]