Green’s Dictionary of Slang

sweetie n.

also sweety

1. [late 19C+] an attractive young woman.

2. [20C+] a beloved child.

3. [1910s+] (orig. US) a boy- or girlfriend.

4. [20C+] a term of address, not necessarily implying intimacy.

5. [1920s+] used ironically to mean an unpleasant person, e.g. He’s a real sweetie; also as adj., unpleasant.

6. [1930s+] a pleasant person.

7. [1960s–70s] an effeminate homosexual.

In compounds

sweetie-pie (n.) (also sweetie-pops, sweet-pie, sweetycakes, sweety pie, twinklepie) [praising the beloved as ‘good enough to eat’]

[1920s+] a general term of affection; a girlfriend.