Meaning

adjective distasteful and unpleasant; spoiled by mixture

adjective slightly salty (especially from containing a mixture of seawater and fresh water)

originFrom Scottish brack (from Middle Dutch brac (“brackish”)) + -ish. Cognate with Dutch brak (“brackish”), German Low German brack, brakerg, brakig (“brackish”), German brackig (“brackish”), Danish brak (“brackish”), Swedish bräck (“brackish”), Norwegian brakk (“brackish”). Perhaps a distant doublet of brook.

Etymology from Wiktionary, CC BY-SA 3.0