Aunt (n)

1. a. The sister of one's father or mother. Also, an uncle's wife, more strictly called an aunt-in-law.

1711 ADDISON Spect. No. 7 {page}4 A Maiden Aunt..who is one of these antiquated Sybils. 1834 GEN. P. THOMPSON Exerc. (1842) III. 45 note, What might have happened afterwards, is only known to those who can tell what would have come to pass if your aunt had been your uncle.

b. (in U.S.) Used endearingly of: Any benevolent practical woman who exercises these qualities to the benefit of her circle of acquaintance; cf. Sp. tia, and see AUNTHOOD. Also used dial. (see E.D.D.) as ‘a term of familiarity or respect applied to elderly women, not necessarily implying relationship’. Also transf. Cf. AUNTIE. (Universal aunt is taken from the name of a bureau in London undertaking such services, e.g. conducted tours, errands, as might be rendered by a maiden aunt. Cf. AUNTHOOD.)

1921 Star 28 Feb. 4/5 (headline) Professional Aunts on Hire.

6. Special collocations: Aunt Edna, used of a typical theatre-goer of conservative taste; Aunt Emma, used in croquet of a typically unenterprising player (or play); Aunt Fanny, in various slang phrases expressing negation or disbelief.

1963 Croquet Aug. 3/1 Aunt Emma is banished for ever. 1967 Ibid. Aug./Sept. 13/2 He played too much ‘Aunt Emma’. 1945 M. DICKENS Thurs. Afternoons i. 69 She's got no more idea how to run this house than my Aunt Fanny.