The oldest profession in the world (or the world's oldest profession) is a phrase that, unless another meaning be specified, refers to prostitution. However, it did not acquire that meaning universally until after World War I. Formerly, various professions vied for the reputation of being the oldest.
The claim to be the oldest profession was made on behalf of farmers, cattle drovers, horticulturalists, engineers, landscape gardeners, the military, doctors, nurses, teachers, priests, and even lawyers.
Perhaps the earliest recorded claim to be the world's oldest profession was made on behalf of tailors. The Song in Praise of the Merchant-Taylors, attested from 1680, which was routinely performed at pageants at the Lord Mayor's Show, London, if the current mayor happened to belong to the tailors' guild, began:
After pointing out that Adam and Eve made garments for themselves, and were therefore tailors, it continued:
Acquisition of opprobrious sense
The phrase began to acquire its opprobrious sense in the last decade of the nineteenth century following Rudyard Kipling's short story about an Indian prostitute, On the City Wall (January 1889). Kipling, after citing a biblical reference, began:
Lalun is a member of the most ancient profession in the world. Lilith was her very-great-grandmamma, and that was before the days of Eve as every one knows. In the West, people say rude things about Lalun's profession, and write lectures about it, and distribute the lectures to young persons in order that Morality may be preserved. In the East where the profession is hereditary, descending from mother to daughter, nobody writes lectures or takes any notice; and that is a distinct proof of the inability of the East to manage its own affairs.
In a scathing article on the morals of the aristocracy in the mass circulation Reynold's Newspaper, 22 July 1894, the reference was repeated:
In ancient Rome, under the empire, ladies used to go to baths to meet a certain class of men, while men resorted thither to meet a certain class of ladies. The ladies belonged to what has been called “the oldest profession in the world", a profession which is carried on in Piccadilly, Regent street, and other parts of London with great energy every night …
In the same year the Pall Mall Gazette reported a speech in which "Mrs. Ormiston Chant … implored us to stand shoulder to shoulder and destroy what Kipling has called 'the oldest profession in the world'".
The phrase was frequently used as a euphemism when delicacy forbade direct reference to prostitution.
Kipling was not the first to employ the phrase "the most ancient profession" in an opprobrious sense. The Irish poet Henry Brooke (1701–1783) wrote:
The phrase had also been applied to murderers. In The Secret Societies of All Ages and Countries (1875), Charles William Heckethorn, describing the Thugs of India, said:
The hierophant, on initiating the candidate, says to him: "Thou hast chosen, my son, the most ancient profession, the most acceptable to the deity. Thou hast sworn to put to death every human being fate throws into thy hand..."
Residual usage of the phrase in its reputable sense
There is some evidence that unworldly speakers (e.g. of the older generation) or unsophisticated audiences (e.g. in small towns or rural areas) were not at first aware of the phrase's newly acquired meaning. Thus for some time the following could be said in English newspaper reports without apparent embarrassment: “A certain proportion of the cadets were now leaving to enter the oldest profession in the world” (1895). “This gentleman's name often figures high in local prize lists, and he is considered an enthusiast in 'the oldest profession in the world'" (1902). “Mr Petrie heard the voice of God and observed the working of His hand in ways that are denied to most of us. His speech, and especially his prayers, exhibited a rare consciousness of the beauty of holiness, and were fragrant with phrases of singular charm. As you all know, Mr Petrie followed the oldest profession in the world” (1915).
However, those 'innocent' uses of the phrase tended to die out as awareness of the newly acquired meaning increased; as did the appreciation that antiquity, of itself, did not make a profession respectable.