Green’s Dictionary of Slang

dingus n.

[Du. ding, a thing]

1. [late 19C+] (also dingis) anything for which one cannot recall the proper name.

2. [late 19C+] a euph. for the penis.

3. [1930s–50s] (US drugs) an improvised hypodermic syringe, made from an eye-dropper and a pin.

4. [1950s–70s] a dildo.

5. (US) a fool, a show-off.