Familiar, affectionate term for one's own mother, similar to 母ちゃん but with the polite prefix お. Used in casual family settings, especially by children or when speaking to children.
See also: 母ちゃん
お母ちゃん、今日の晩ごはんなに？
Mum, what's for dinner tonight?
うちのお母ちゃんは料理が上手やねん。
My mum is good at cooking.
お母ちゃん adds the polite prefix お to 母ちゃん, making it a slightly softer, more affectionate way to address one's mother.
Derived from 母 (かあ) with the familiar suffix ちゃん and the polite prefix お. The exact historical development is uncertain, but it is a natural affectionate variant of お母さん.