Malay/Javanese origin. Bleeker (1850, 1858) indicates Ikan Wadder Bettah as the local name of Betta trifasciata Bleeker, 1849 (now Betta picta, Valenciennes, 1846) in the Ambarawa Javanese dialect. Ikan Wader is a common Javanese name for smaller freshwater fishes, especially cyprinids (already used in Old Javanese). See Blust, R. & Trussel, S. Austronesian Comparative Dictionary. Web Edition (https://www.trussel2.com/acd/).
From the Latin stigmosus, meaning full of marks, referring to the patterned opercle and barred pattern on dorsal, caudal and anal fins of both male and female specimens.