Definition from Wiktionary, the free dictionary
From a former name of the church's program for young women, which was the Young Women's Mutual Improvement Association, or YWMIA. First adopted and applied to the middle age group of the YWMIA in 1950.
Mia Maid (plural Mia Maids)
See also 
- Priesthood and Auxiliary Leaders’ Guidebook, p. 11 "Auxiliaries."