Is it farther or further?
early 13c., "to shy, start," perhaps from shunen "to shun" (see shun), and altered by influence of shot or shut. Meaning "to turn aside" is from late 14c.; that of "move out of the way" is from 1706. Adopted by railways from 1842. Related: Shunted; shunting.
1838, in railway use, from shunt (v.). By technicians in the sense of "electrical conductor" from 1863. Medical use dates from 1923.
A passage between two natural body channels, such as blood vessels, especially one created surgically to divert or permit flow from one pathway or region to another; a bypass.