of water, "somewhat salty," 1530s, from Scottish brack "salty" (see brack) + -ish. Related: Brackishly; brackishness.
Entries linking to brackish
brack adj.
"salty, briny," 1510s, from Dutch brak "brackish," probably from Middle Dutch brak "worthless," a word also used in commercial trade and which also made its way into early Modern English.
-ish
adjectival word-forming element, Old English -isc "of the nativity or country of," in later use "of the nature or character of," from Proto-Germanic suffix *-iska- (cognates: Old Saxon -isk, Old Frisian -sk, Old Norse -iskr, Swedish and Danish -sk, Dutch -sch, Old High German -isc, German -isch, Gothic -isks), cognate with Greek diminutive suffix -iskos. In its oldest forms with altered stem vowel (French, Welsh). The Germanic suffix was borrowed into Italian and Spanish (-esco) and French (-esque). Colloquially attached to hours to denote approximation, 1916.
The -ish in verbs (abolish, establish, finish, punish, etc.) is a mere terminal relic from the Old French present participle.