Green’s Dictionary of Slang

iron n.

[later use is US]

1. [16C–early 18C; 1930s+] the penis.

2. as a metal coin.

(a) [late 18C–1920s] money.

(b) [1900s–10s] (US) $1 in cash.

3. as a metallic object.

(a) [early 19C–1910s] (US) bullets or shells.

(b) a sword.

(c) [mid-19C+] (US, also fire-iron, piece of iron) a gun.

(d) [1920s] (US Und.) a drill bit.

(e) [1920s+] (US prison) handcuffs.

(f) [1930s+] (US) a discontinued model of motor car, a run-down, dilapidated car.

(g) [1940s] a housebreaker’s implement, a crowbar.

(h) [1960s–70s] (US) a motorcycle.

(i) [1970s+] (US) weights, as used in bodybuilding exercises.

(j) [1970s+] a knife.

4. [mid-19C; 1990s+] in fig. use, courage.

5. [1980s+] (W.I., Jam.) a thug, a gangster.

In compounds

iron boy (n.)

[1910s–20s] (US) $1.

iron dollar (n.) (also iron buck)

[late 19C–1920s] (US) $1 in cash.

iron freak (n.) [-freak sfx]

[1960s] (US) a weight-lifting enthusiast.

ironhead (n.)

[1990s+] (US prison) one who works out with body-building weights.

iron louie (n.)

[late 19C] (US) $1.

iron man (n.)

1. [20C+] (US) $1; usu. in pl.

2. [1940s–60s] (US) $1000.

3. [1940s–70s] (orig. Aus.) £1 note.

iron-whip (v.)

[1970s] (US Und.) to pistol-whip.

In phrases

carry iron (v.)

[1930s] (US Und.) to go armed, esp. as a gangster’s bodyguard.

eat iron (v.)

[1920s] (US prison) to spend time in a cell.

fire-iron (n.)

see sense 3b above.

iron out (v.)

[2000s] of money, to spend freely.

lay some iron (v.)

[1930s] (US Black) tap-dancing.

piece of iron (n.)

see sense 3b above.

pump iron (v.) (also bump iron, drive..., throw...)

[1960s+] (orig. US) to work out with weights, to practise bodybuilding.

push iron (v.)

[1960s–80s] (US) to exercise with weights.

put an iron on one’s shoulder (v.)

[1980s+] (N.Z.) to become indebted, lit. or fig.