1736, "water or liquid thrown upon anything," from splash (v.). Meaning "striking or ostentatious display" is first attested 1804. Sense of "small quantity of soda water, etc., added to a drink" is from 1922. Of color or light, 1832.
adjective suffix, "full of or characterized by," from Old English -ig, from Proto-Germanic *-iga- (source also of Dutch, Danish, German -ig, Gothic -egs), from PIE -(i)ko-, adjectival suffix, cognate with elements in Greek -ikos, Latin -icus (see -ic). Originally added to nouns in Old English; used from 13c. with verbs, and by 15c. even with other adjectives (for example crispy).
<a href="https://www.etymonline.com/word/splashy">Etymology of splashy by etymonline</a>
Harper, D. (n.d.). Etymology of splashy. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/splashy