The Young Sheldon Episode That Explains Why TBBT's Sheldon Says 'Coitus'

Physical intimacy is always an uncomfortable topic for Sheldon Cooper (Jim Parsons) on "The Big Bang Theory." Simply holding hands with Amy Farrah Fowler (Mayim Bialik) is a huge deal, let alone anything more. In fact, his use of the word "coitus" to refer to the act of sex makes it sound as unromantic as possible. But how and when did he start using this particular descriptor?

"Young Sheldon" Season 5, Episode 6, "Money Laundering and a Cascade of Hormones," reveals the origin of "coitus." After Missy (Raegan Revord) asks personal questions of her crush Pastor Rob (Dan Byrd) in Sunday school class, Mary (Zoe Perry) awkwardly tries to give her and Sheldon (Iain Armitage) "the talk." Sheldon then decides to browse his thesaurus and find a less-taboo word for "sex" to use in such conversations.

Adult Sheldon says in narration, "In our society, any discussion of human reproduction seems to be so upsetting, it causes nothing but chaos: lost jobs, lost friends, sleepless nights. Even the word 'sex' provokes an uncomfortable reaction. I thought 'fornicate' might work, but that seemed too judgy. Then I found the perfect word, a word so bland and clinical that it would be impossible to take offense to it." Thus, "coitus" was born.

After a lifetime of distancing himself from the emotional messiness that he associates with physical intimacy, Sheldon Cooper (Jim Parsons) finally partakes in "coitus" in "The Big Bang Theory" Season 9, Episode 11, "The Opening Night Excitation." Quite shockingly, he chooses an evening with birthday girl Amy Farrah Fowler (Mayim Bialik) over seeing the new "Star Wars" flick with his friends. In fact, it's decided that coitus will occur on her birthday each year.

According to co-creator Chuck Lorre, this arrangement shows that Sheldon's mindset toward coitus hasn't changed much since adolescence — though he enjoyed himself, he still doesn't understand the hype that society places around intimacy. "Sex plays a very small part in his life, and I've always found that to be one of the most wonderful things bout [sic] Sheldon's character: that he opted out of that part of life that everyone else assumes we should be obsessed with. He's chosen not to be. From the very beginning, it's just not something that holds a lot of interest for him," Lorre told The Hollywood Reporter.