Brit. sp. salt′pe·tre
Origin of saltpeteraltered (infl. by salt) ; from Middle English salpetre ; from Middle French ; from Medieval Latin sal petrae, salt of rock ; from Classical Latin sal, salt + petra, rock
See potassium nitrate.
Origin of saltpeterMiddle English salpetre, from Old French, from Medieval Latin salpetrae : Latin sal, salt; see sal- in Indo-European roots + Latin petrae, genitive of petra, rock (from Greek petra; see per-2 in Indo-European roots).