kitchen supper

Etymology
. Original use from kitchen as a synecdoche for a household's servants. Later from the idea that the hosts forgo the dining room for the more private and relaxed kitchen.

Noun

 * 1)  The evening meal for servants, separate from the family's meal.
 * 2) An informal or semiformal meal served for guests, not necessarily one served in the kitchen.
 * 1) An informal or semiformal meal served for guests, not necessarily one served in the kitchen.

Usage notes
In contemporary British use, the phrase is seen as snobbish and very U. Charles Moore in The Daily Telegraph describes it as "disclosing an assumption – we have a nice dining room but we’ll be all relaxed with our pals and won’t use it – which is perplexingly, excludingly foreign to [a general] audience", while Harry Mount says that "[although] the ingredients of a kitchen supper are universally recognisable [...] the actual expression is confined to the upper-middle classes".