The story
- Proto-Indo-European*sḗh₂l
- Proto-Italic*sāls
- Latinsāl
- Ancient Greekπέτρᾱ (pétrā)
- Latinpetrae
- Medieval Latinsāl petrae
- Old Frenchsalpetre
- Middle Englishsaltpetre
- English todaysaltpetre
From Middle English saltpetre, alteration of Old French salpetre, from Medieval Latin sāl petrae (“salt of the rock”), named so being found as an incrustation. Alteration of the first element is from folk-etymological association with salt (which is, nevertheless, cognate to Latin sāl).
Words from the same roots
Old Frenchsalpetre all →
peter
Etymology from Wiktionary, CC BY-SA 4.0.