Of native Korean origin. Compare Old Japanese母 (omo, “mother; wetnurse”).
This entry lacks etymological information. If you are familiar with the origin of this term, please add it to the page per etymology instructions. You can also discuss it at the Etymology Scriptorium.
Particularly: “How is this related to 어머니 (eomeoni)? Is 어머니 (eomeoni) a compound of 엄마 (eomma) + suffixing element 니 (ni), or is 엄마 (eomma) an abbreviation of 어머니 (eomeoni)?”