A hueco is a depression eroded into a rock that will often stand water long after everything else has gone dry. It’s a naturally occurring stone tank, essentially, usually elevated simply because that’s where the exposed stone is. In the Old West of westerns, huecos saved countless parched cowboys and allowed whole bands of Indians to keep to trails that, due to an apparent lack of water, seemed otherwise impossible. Temporary (reliant on rain) and often purposely poisoned with a dead animal, however, huecos marked the end for perhaps just as many. The term itself translates from the Spanish to “hollow” or “cavity,” and seems to carry with it the idea that a hueco is recessed, hidden, nearly inaccessible—behind something else. Which, for it to stand water for any length of time, is necessary: with no shade, the water would quickly evaporate. Another spelling of hueco is waco, as in the Waco (Wichita) Indians of the Brazos and Guadalupe Rivers of Texas, rivers that, in many places, have wide stone beds pocked with little hollow bowls, seemingly made to hold handfuls of water. Waco, Texas, is of course named after these Waco Indians; Hueco Springs, Texas, and Hueco Tanks State Historic Site, also in Texas, come by their names more directly.