One characteristic of the jargon of particular trades or professions is that they appropriate words which have a well-understood literal meaning and adapt them to describe some technicality. Footfall is a good example. It has been taken up by the retailing industry to refer to the number of people entering a store, a direct equivalent of the older show business cliché bums on seats (tourism marketers have a similar term, bums on beds). So you might read in an article that “The Trocadero has an annual footfall of 16 million visitors”. If you have a high footfall, you are presumably doing well (though the concept wisely does not attempt to equate the numbers who buy with the numbers who enter), so the ambition of all retailers is to increase their footfall. A letter to the British Bookseller magazine recently noted that at least one of the more aggressive marketers has begun to speak of driving footfall, as in “We strive to show booksellers what we are doing to support them and drive footfall into their stores”, which raises a disquieting image of the marketer as sheepdog, herding his charges towards the point of sale. I’ve seen footfall only in UK sources, so it may be a peculiarly British term. If so, do please forgive us for inventing it.