Green’s Dictionary of Slang

speak v.

also speak to, speak with
[ironic euph.]

1. [early 18C–mid-19C] (UK Und.) to hold up; to rob; to steal.

2. (UK Und.) to pass sentence of death.

3. [late 19C] (Aus.) to select one’s drink.

SE in slang uses

In phrases

on speaks (also playing speaks)

[1900s–20s] (UK society) on speaking terms.

speak bandog and Bedlam (v.)

see under bandog n.

speak brown tomorrow (v.)

[late 19C] to get sunburned.

speak holiday (v.) [SE holiday; thus the image of one’s ‘best’ language]

[late 16C–early 17C] to speak elegant, formal English.

speak like a mouse in (a) cheese (v.)

[late 17C–early 19C] to speak quietly or indistinctly.

speak on the big white telephone (v.)

see under telephone n.

speak pound notes (v.) [the assumed correspondence of wealth and ‘good’ English]

[1980s] (Irish) to speak Standard English.

speak pretty (v.)

[late 19C–1910s] (mainly Aus.) to speak in an affectionate, friendly manner.

speak proper (v.) [abbr. speak proper English or, thus ironically, misusing proper in place of properly]

[20C+] to talk in Standard English, rather than in colloq., dial. or sl., often as an imper.

speak Welsh (v.) [echoic]

[1990s+] to vomit.

speak white (v.)

[1960s+] (Can.) used by English speakers, to speak English (as opposed to French, which is the first language of many Canadians, esp. the Québecois).