Antoine Banier
Antoine Banier was a French clergyman (1673–1741) and seems to have been the first author to have used the term "involuntary celibacy" within the corpus of books that are searchable on Google Books. It could well be that even older documents mention this term or a very similar one, which may have been lost, not digitalized or wrongly digitalized etc. Anyhow, this proves inceldom is not a new phenomenon at all such that others have come up with the term, possibly multiple times throughout history, and long before it was used in the social sciences.
In a 1739 book he described inceldom as a form of imprisonment which he referred to as "yoke". He also described it as a form of suffering and anguish, as "groan". The term was used in the following excerpt from The Mythology and Fables of the Ancients, Explain'd from History, Volume 3:[1]
The custom of the Ancients in their marriages was quite different from that of the age wherein we live: large gratifications were given to the young ladies whom they were to marry, and even to their parents, whereas it is very rare now-a-days for one to marry a woman without a portion. Homer and several others, mention this Custom, and would to God it were still in Fashion: How many young Women who groan under the Yoke of involuntary Celibacy, would find Husbands to make them happy, did not the Avarice of those husbands reduce them to the calamities wherein ixion was involved.
—The Mythology and Fables of the Ancients, Explain'd from History, Volume 3
The "calamities of ixion" refers to the mythical Greek King of Thessaly, Ixion, who refused to pay the bride-price owed to his father in law, leading to Ixion eventually treacherously murdering the father-in-law, becoming the first kin-slayer and thus an outcast.[2] Banier is referring to the ancient custom of bride price (man paying the woman's family to be married) as being preferable to the contemporary European custom in his own era of the dowry. The dowry is a sum paid by the woman's family to the man, as this was seen as essential 'seed capital' that established a stable marriage, and also because women were often seen as such a useless burden that men would have to be incentivized to marry them. Some have claimed that the dowry also served as an incentive to induce upper-class men to marry less physically attractive upper-class women, instead of marrying prettier lower class women. This would have maintained the integrity of the class systems in place in Europe at the time.