"to stop the flow of" (especially of blood), early 14c., from Old French estanchier "cause to cease flowing (of blood), stop, hinder; extinguish (of fire); tire, exhaust, drain" (Modern French étancher), from Vulgar Latin *stancare, perhaps contracted from *stagnicare, from Latin stagnum "pond, pool" (see stagnate). But Barnhart says it probably is from Latin stantio, present participle of stare "to stand."