It is an AmE informal expression according to ODO:
- Meet for lunch.
‘you're a doll—we'll do lunch!’
The expression is from the 1970s according to Grammarphobia, and it is just an extension of the versatile and very common verb to do in expressions like: “do sushi”, “do coffee” and “do alcohol”.
We’ve all heard it for years now, from “Let’s do lunch” to the eternal refrain of cleaning people everywhere: “I don’t do windows.”
In fact, from a historical standpoint, this kind of construction— “do” followed by a noun as direct object—isn’t unusual. For more than a thousand years, English speakers have used it to mean achieve, perform, bring about, carry out, accomplish, and so on.
“Do” is extremely useful in this way. As the Oxford English Dictionary remarks, “Since every kind of action may be viewed as a particular form of doing, the uses of the verb are as numerous as the classes of objects which it may govern.”
A related sense, “to eat or drink, esp. habitually,” dates from the 1970s, Oxford says. The dictionary’s citations include “do booze” (1970), “do sushi” (1987), “do coffee” (1989), and “do alcohol” (1994). We might add your example “do quiche” (as in “Does he do quiche?”).
As we also mentioned in that earlier post, “do lunch” is vintage 1970s. This expression (sometimes it’s “do dinner”), was first recorded in Ladies’ Man (1978), a novel by Richard Price:
- “ ‘Kenny, whata you doin’ now?’ ‘Now? I was gonna do lunch; you wanna do lunch?’ ”
Probably its popularity is due to its usage in informal business contexts with the meaning: "let's meet for lunch;"
The OED defines the phrase as meaning “to meet for the specified meal, esp. with a view to conducting business.”
This more businesslike exchange of pleasantries is from Marc Blake’s novel 24 Karat Schmooze (2001): “ ‘And if you come up with something more, do get in touch.’ ‘I will.’ ‘We must do lunch.’ ”
The business context, specifically the entertainment one, is confirmed also by the www.barrypopik site:
"Let’s do lunch” (meaning “let’s get together for lunch and discuss this") was popularized from 1985 in the business speak of the entertainment industry in Los Angeles. The phrase quickly became overused and “Let’s do lunch—I’ll call you” became a way to brush someone off forever.
One citation of “let’s do lunch” exists from 1955, however, and is credited to “smart-talk boys... in the white-collar canyons of Manhattan.”
- “Let’s do lunch...it’s on me” has become newly popularized as a saying on baby bibs.