staunch (adj.)

early 15c., "impervious to water," from Old French estanche "firm, watertight," fem. of estanc "tired, exhausted, wearied, vanquished; water-tight; withered, dried" (Modern French étanche), from Vulgar Latin *stanticare (source also of Spanish estanco "water-tight," Italian stanco "exhausted, weary"), probably from Latin stans (genitive stantis), present participle of stare "to stand," from PIE root *sta- "to stand, make or be firm." Sense of "strong, substantial" first recorded mid-15c.; of persons, "standing firm and true to one's principles" from 1620s.

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Definitions of staunch from WordNet
staunch (v.)
stop the flow of a liquid;
staunch the blood flow
Synonyms: stem / stanch / halt
staunch (adj.)
firm and dependable especially in loyalty;
a staunch defender of free speech
Synonyms: steadfast / unswerving