also round-house, "lock-up, place of detention," 1580s, from Dutch rondhuis "guardhouse." Meaning "circular shed for locomotives with a turntable in the center" is from 1856. Meaning "blow delivered with a wide sweep of the arm" is perhaps extended from "round building for circular machinery."
roundabout
roundel
roundelay
rounder
Roundhead
roundhouse
roundness
round-table
roundup
rouse
rouser