canaigre

from The Century Dictionary.

• noun In Texas, a species of dock, Rumex hymenosepalus, the root of which is used in tanning.
• noun It is native on the arid plains from Texas to California, and has become prominent as a commercial source of tannin. The tuberous roots contain about 35 per cent. of tannic acid. These had long been utilized by the Mexicans as a medicine and for tanning saddle-leather when an export trade in them was started, at first in bulk, then as dried chips, then as extract. The natural supply being insufficient, cultivation with irrigation has been undertaken on a large scale.