Green’s Dictionary of Slang

hairpin n.

1. [late 19C+] (US) a fool, a simpleton.

2. [1920s–60s] (US) a woman.

3. attrib. use of sense 2.

4. [1950s] (US, also hair-bones) a thin person.

5. [1950s] (Aus.) a despised person.

In phrases

drop hairpins (v.)

see separate entry.