the.com/blockhouse

means A small, heavily built fortified structure—often of timber or concrete with thick walls and gun slits—used as a defensive strongpoint or lookout.

from Traces to 16th-century military usage, combining 'block' (a solid, massive chunk) with 'house.' The name describes exactly what it was: a blocky, squat structure, unlike the airy castles and towers around it, built low and thick to shrug off cannon fire and musket shot. The word later traveled into American frontier vocabulary for the log strongholds settlers built against raids, and into naval and railway jargon for small armored or signal-control shelters.