Word Origin & History
1579, reduplication of *ma-, nearly universal among the I.E. languages (cf. Gk. mamme "mother, grandmother," L. mamma, Pers. mama, Rus., Lith. mama "mother," Ger. Muhme "mother's sister," Fr. mamen, Welsh mam "mother"). Probably a natural sound in baby-talk, perhaps imitative of sound made while sucking.
In educated usage, the stress is always on the last syllable. In terms of recorded usage in Eng., mum is from 1823, mummy 1839, momma 1884, mom 1894, and mommy 1902.