Green’s Dictionary of Slang

buddy n.

[SE brother or dial. butty; itself ult. obs. SE booty, sharing; however, note earlier bud n.1 ]

1. [late 18C+] (orig. US, also buddie) a form of address to a male.

2. [mid-19C+] (orig. US, also buddy-cat, buddy-roo) a friend, an acquaintance.

3. [1970s+] (W.I./UK black teen) a sexual partner.

4. [1990s+] (US/W.I.) the penis.

In derivatives

buddy-o (n.) (also buddy-roe, buddy-roo) [-o sfx (1)]

[1940s+] (US) an affectionate or ironic term of address.

In compounds

buddy boy (n.)

[1950s+] (orig. US) a friend, usu. in a negative or ironic use; esp. as a term of address.

buddy-cat (n.)

see sense 2 above.

buddy-gee (n.) (also buddy-ghee) [gee n.3 (1)]

[1930s–60s] (US black) a friend, a man.

buddy seat (n.)

[1940s–60s] the pillion seat on a motorcycle.

buddy sex (n.)

[2000s] (US gay) hedonistic sexual intercourse without committment.