Alright, I’m going to answer this question, even though it is highly tangential to my studies and I hate popular threads, because I’m both mad that no one’s answered this properly because it’s a valid question (and very obvious if you know it) and apparently I’m plumb crazy this morning.

It’s going to be very difficult to prove this didn’t ever happen (individual people have all sorts of sex all over the world, though I mean, how on earth is your man Jeeves supposed to accurately sense your time of crisis?), but it’s very easy to talk about why you heard this rumor in 2016, and what this rumor means to religious history. This story is just example #1506 of the fine art of Anti-Catholicism. Protestant accusations, jokes, and rumors of the sexual deviancy of Catholics is a very old game. Sex actually has it’s own sub-heading on the Wikipedia page for anti-Catholicism. It’s also not exclusive to Protestants vs. Catholics, for example the occasional resurgence of the story about people of XXX religion having sex through a hole in the sheet often is paired with seemly random religious minorities, I’ve even heard the “holy holey sex” story applied to Muslims in recent years. It takes very little work for people to believe the religious Other is weird and bad, and naturally therefore, they have weird and bad sex. So this idea of Catholics doing this particular crazy sex thing has to get in line behind a lot of other stories about how Catholics are having unnatural sex. (It can also be hard to tease out anti-Catholicism in history, because it gets muddled with sentiments of anti-Italianism, anti-Irish, anti-immigrant, these days anti-Latino, etc. etc., I have only approached it from the anti-Italianism angle.)

The flavor of the sexual deviancy, however, varies. Before the birth control debates started, there was more prurient interest in the religious celibate, because Protestants do not have celibate religious leaders. However, as over the last 100 years or so, as mainstream Protestant sects of Christianity have accepted non-abortion methods of birth control, Catholics notably (officially) do not. This is a somewhat recent divide, and I’d be surprised if this story about knocking-to-avoid-knocking-up appeared before the divide between Catholics and Protestants on birth control as a Christian issue. Both of them, interestingly enough, also play into Protestant feelings on the sacredness of Family, but in different ways; the first that celibacy denies Christians a healthy family life, the second that lack of birth control denies Catholics “correctly-sized” families and makes them poor, as Western mainstream Christians have embraced smaller families… But this story plays perfectly into two classic anti-Catholic stereotypes: that their religious beliefs about sex are strange and impractical to real life, and that Catholics are hypocritical and happy to “cheat” on their religious beliefs. Thus you have a story where a Catholic couple farcically cheats on their sexual morals by having a third party privy to their sex act. It’s some straight anti-Catholic gold really. So we hear it, cue some Protestant lols, and then promptly get back to Work Ethicking or whatever.

I’m not saying you or your friends are anti-Catholic, because it’s totally possible to pass around a joke or rumor without knowing what it means, and you were 100% a Good Critical Thinker to run to Google and then AskHistorians to try to see if it’s real. But now you know what it means, and why therefore it’s hard to google. :/

Interesting question. As a practicing Catholic who has taught Church teaching as a youth minister and missionary, I have not heard of Coitus Interruptus as an acceptable method of birth control at any point. I decided to do some research. Here's what I found:

Reading the Papal Encyclical Humanae Vitae, a Church document which addressed topics of Catholic contraception in light of the changes in modern society at the time, Pope Paul VI writes

"Similarly excluded is any action which either before, at the moment of, or after sexual intercourse, is specifically intended to prevent procreation—whether as an end or as a means (par 16)."

The text here is clear that any action, be it the use of barriers, pills, or even interruption (since the interruption itself is planned and intentional) is sinful and to be avoided. Of course, Humanae Vitae was published in 1968, so while it offers a clear explanation of what the Church has and continues to teach, it does not help look at any customs or practices closer to the time frame the OP is asking about.

To look further into the past, we can examine a passage of scripture from the Bible’s Old Testament. In Genesis, there is a story of Onan, who, after his brother died, married his wife as according to Jewish law. However, when they went have sex, Onan performed Coitus Interruptus and God was displeased by this and took Onan’s life (Genesis 38:8-10 NASB). This scripture would contribute to Christian’s, Catholic and Protestants alike, arguments against contraceptive practices until the 1930s, when the Anglican Church moved to make contraceptives acceptable in certain cases (Wikipedia). In the Catholic tradition, the Pontifical Council for the Family asserts in Vademecum for Confessors that

“the Church has always taught the intrinsic evil of contraception, that is, of every marital act intentionally rendered unfruitful (2:4).”

Judging by what’s available, or at least immediately available within reason, on the internet I cannot find record of the act that you’re talking about. Based on what I’ve found and what I already know about the Catholic Church, I find it difficult to think that this was ever an encouraged or condoned practice (that's not to say that the act you describe never happened. In a world with billions of people, it's almost certainly happened dozens of times). I say this because, as stated in the above quotes, contraception is seen by Catholics as anything which results in the unnatural ending of sexual intercourse, i.e. that either the semen is, in some way, prevented from entering the woman’s body by natural means (whether by condoms, diaphragms, or “pulling out”) or through preventing fertilization by chemical means.

The above is the result of my research and application of what I understand about Church teaching. What follows is my speculation. It is not Church teaching and is purely my own reasoning base off of what I k. Take it with a grain of salt (or a pile of salt).

I would say that it is possible (and likely) that whatever you read was not an authoritative document of the Church, but perhaps someone who had attempted and believed they did find a loophole (which is very interesting for someone like myself who has a deep interest in moral theology. I would love to read it to understand their rationale). I imagine that the person’s rationale went something like this: when interrupted during sexual intercourse, this can disturb the conjugal act and, through no fault of the man or woman engaged in sex, render them in able to complete the sexual act (that is to say, there can be no ejaculation). However, having someone intentionally disturb the couple engaging in intercourse would itself be a planned, premeditated form of contraception in an attempt to remove any obligation from the participants in the sexual act. Because it’s premeditated and intends to render the sexual act unfruitful, it is still a form of contraception.

Hope this helps and I hope someone else can shed some more light into this.

Hello everyone,

I'm going to interrupt the current stream of comments here and remind everyone that this is AskHistorians, a place for experts to provide answers, not for comments based only on speculation and attempts at 'humour'. Contrary to our rules, in this thread there have been a large number of incorrect, speculative, or otherwise disallowed comments, including many asking about the deleted comments, which merely compounds the issue. As such, they were removed by the mod-team. Please, before you attempt answer the question, keep in mind our rules concerning in-depth and comprehensive responses. Answers that do not meet the standards we ask for will be removed and repeat offenders will be banned.

Additionally, it is unfair to the OP to further derail this thread with off-topic conversation, so if anyone has further questions or concerns, I would ask that they be directed to modmail, or a META thread. Thank you!