Origin of swell box
Examples from the Web for swell box
The organist might leave his Swell-box shut or, by means of a catch on the pedal, hitch it full open.The Recent Revolution in Organ Building|George Laing Miller
Choir organ, of soft, mellow stops, often enclosed in a swell-box.
Echo organ, of stops of small scale and very soft tone, enclosed in a "swell-box."
The swell-box is made in three thicknesses, each of one inch.Bell's Cathedrals: The Abbey Church of Tewkesbury|H. J. L. J. Mass