Green’s Dictionary of Slang

Pat n.

[var. on Paddy n.; the two senses here, while of differing national origins, are both immigrants]

1. [late 18C+] a generic term for an Irishman; also as a term of address or nickname.

2. [1900s-50s] (Aus.) a Chinese person.

3. [1990s+] (Irish und.) as Pat’s, St Patrick’s Institution, an Irish equivalent of Borstal.

In compounds

Patland (n.)

1. [mid-19C–1900s] Ireland.

2. attrib. use of sense 1.

Patlander (n.)

[early 19C–1900s] an Irish person.

pat wagon (n.) (also patty wagon) [negative stereotyping]

[1900s–30s] (US) a vehicle in which prisoners are conveyed to a police station (cf. paddy wagon under Paddy n.).

In exclamations