Seltzer

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mid 18th century (denoting a type of naturally effervescent mineral water): alteration of German Selterser, from Selters, the name of a German village near which this water was obtained.

wiktionary

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A toponym from 1735–45 German Selterser(“of Selters”), after Selters, a village known for its carbonated mineral springs.

etymonline

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seltzer

1741, from German Selterser (Wasser), a kind of mineral water, literally "of Selters," village near Wiesbaden in Hesse-Nassau, where the mineral water is found.