In the eighteenth and nineteenth century in Europe and America, a calling card, or visiting card, was an aspect of etiquette among the moneyed classes. If you had not been invited to visit someone and you wanted to see them in their home, you would first come by and leave a card with the domestic servant who answered the door. If the person wanted to see you, they would send their card in return, signalling that you were welcome to call.

In O. Henry's story, it is implied in the quotation that even though Billy McMahan's wife had an elegantly engraved visiting card, there were people who considered themselves above her and her husband who would not send her a visiting card in return. The tacit message would be that she would not be admitted to call. The implication is that even though Billy McMahan had some wealth and social power, it was not without its limits.

In the short story 'The Social Triangle' by O. Henry, the author makes reference to small cards he calls 'visiting cards.' In other societies, such as in England, these cards were also called 'calling cards.' Their purpose was to introduce a visitor to the household and observe social niceties such as the accurate representation of exactly who it was that had called should the householders not be 'at home.' This was important because the practice was mainly found within the 'higher' social classes. there was a strict social etiquette attached to visiting with folks at that time. For example, a lady could decide not to be 'at home' to visitors on a certain afternoon. It is significant because often these classes had servants to answer the door and introduce guests. The visitor did not have to impart complicated descriptions to the butler/maid but just leave their 'calling card' if there was no letter box, for example.