As seen in the photos below, some businesses and a church include "Cotaco" in their names. Off Alabama 36, down Cotaco School Road, is the Cotaco School; scroll down to the bottom of the website "About" page for the "Legend of Cotaco School." Also in the area is Cotaco-Florette Road and Cotaco Creek, which begins in Marshall County and flows into the Tennessee River. Way over in Decatur there is even the Cotaco Opera House, apparently the first opera house constructed in Alabama.
William A. Read's Indian Place Names in Alabama  notes that a Cherokee village probably existed in the area and that "Cotaco" is perhaps a corruption of a Cherokee word for swamp or thicket. The Alabama Territorial legislature in 1818 named what is now Morgan County as Cotaco County; the name was changed in 1821.
I checked some Alabama highway maps from the 1920s until the present and none had Cotaco marked. Yet small places can have much larger resonances through Alabama history.
This business is no longer operating, but the church and grocery below definitely are.