Late 19th century; earliest use found in The Atlantic Monthly. From Italian opera semiseria from opera + semiseria, feminine of semiserio from semi- + serio, after opera seria.
Definition of opera semiseria in US English:
opera semiseria
nounˌɒp(ə)rə sɛmɪˈsɪərɪə
Serio-comic opera.
Origin
Late 19th century; earliest use found in The Atlantic Monthly. From Italian opera semiseria from opera + semiseria, feminine of semiserio from semi- + serio, after opera seria.