staunch

From Middle English staunch, staunche (“(adjective) in good condition or repair; solidly made, firm; watertight; of a person or wound: not bleeding; certain; intact; (adverb) firmly, soundly”) [and other forms], from Anglo-Norman estaunche, Old French estanche (“firm; watertight”) (modern French étanche (“airtight; watertight”)), a variant of estanc (“a pond”), from estanchier (“to stop the flow of a liquid (blood, water, etc.); to make (something) watertight; to quench (thirst)”) (modern French étancher), possibly from one of the following:

From Vulgar Latin *stagnicāre, from Latin stāgnum (“piece of standing water, pond; fen, swamp”), possibly from Proto-Indo-European *steh₂g- (“to drip; to seep”).

From Vulgar Latin *stānticāre, from *stānticus (“tired”), from Latin stāns, stāntis (“standing; remaining, staying”). Stāns is the present active participle of stō (“to stand; to remain, stay”), ultimately from Proto-Indo-European *steh₂- (“to stand (up)”).

See stanch (etymology 4).