Выражение встречается в следующем контексте:

He had very good manners, and the presence of a junior minister. He could, at any moment, be all things to all people. He could talk racing shop, cricket, foreign politics, tell anecdotes of royalty, give motor show information, knew the most interesting plays on at present, advise on places Americans ought really to see in England however short their stay. He had knowledgeable information about where it would suit persons of all incomes and tastes to dine. With all this, he did not make himself too cheap. He was not on tap all the time. Miss Gorringe had all the same facts at her fingertips and could retail them efficiently.

From Agatha Chrisitie's boos "At Bertram's Hotel"

Заранее спасибо