One of the early novels that might be considered to have such elements is 'Tristram Shandy' by Laurence Sterne. Sterne was known for his experimental and rather risqué writing at times. His use of language was quite bold for his era, and there are some expressions in the novel that could be seen as edging towards what we might now consider curse - like language in terms of their irreverence and earthiness.
It is often considered that 'The Canterbury Tales' by Geoffrey Chaucer contains some bawdy and rough language that could be considered precursors to modern curse words. Chaucer was very observant of different social classes and their speech, and in his work, he included language that was closer to the real talk of the people at that time, which might include some words that are not so polite by today's standards.
Some might also point to certain works of Henry Fielding. His novels, like 'Tom Jones', were quite realistic in their portrayal of society. Fielding didn't shy away from depicting the coarser aspects of life, and there could be some language in his works that was on the verge of being what we'd today call curse words, as he was trying to capture the full range of human behavior and speech.
Chapter 340, "Seclusion, the Growing Yu Generation, Family Banquet, Rapid Development (Part 4)", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. The chapter turns that into something concrete by moving from Xia Hong made up his mind and withdrew his gaze, looking through the... to Xia Hong raised the cup and drank it all in one go, his cheeks....
Chapter 8, "Is He Shameless?", is the clearest early answer because it turns Mrs's situation into a concrete plot event.
Chapter 234, "Chasing Wind Youth", is the clearest early answer because it turns Chasing Wind Youth's situation into a concrete plot event. The chapter gives readers a real answer by opening on Given the vast mystical powers Jiang Li had displayed before, he was...
Chapter 34, "Official Recording!", is the clearest early answer because it turns Su Yinwan's situation into a concrete plot event.
Chapter 338, "Rapid Progress, Martial Arts Skills, Dual-Faceted Eastern Expansion, Dormancy Period", is the clearest early answer because the violence around Yangyuan Pill becomes final instead of hypothetical. The chapter gives readers a real answer by opening on Fifty-four鬃, not even a month, twenty-three days, and I even spent... and ending on Of course, there are two difficulties..
Chapter 348, "Zhu Ling in Dire Straits, Eight Camps Martial Contest, Betting Five Years—East Ridge Has Fallen!", is the clearest early answer because it turns Zi Qiang's situation into a concrete plot event. Early on, Even more fatal, the Inspector He Wuyang has since been colluding.... By the end, Calculating for the year, the 60% tribute target equals 72 pounds of.... Inside the broader power growth storyline, the chapter closes with There was no choice;
Chapter 348, "Zhu Ling in Dire Straits, Eight Camps Martial Contest, Betting Five Years—East Ridge Has Fallen!", is the clearest early answer because it turns Beining Mountain's situation into a concrete plot event. It opens with If you defend or attack the stage successfully, you can earn one... and closes on This only made Zhu Tong angrier..
Chapter 341, "Moao's Nine Garrisons, the Inspection System and Zhenyu, Li Hu and Hong Yuru (Part 4)", is the clearest early answer because it turns Zhu Tong's situation into a concrete plot event. It opens with After explaining the general situation he had seen, Lu Yang's brows... and closes on None of them had been to Beishuo before, and it was unlikely that He....
Chapter 60, "The Human Oil King", is the clearest early answer because it turns Seeing Jiang Li's situation into a concrete plot event. The chapter gives readers a real answer by opening on What's with Jiang Yan, treating his own sister Jiang Li like this?"...
Chapter 31, "Master, I've been having some bad luck lately!", is the clearest early answer because it turns Jiang Shi Xu's situation into a concrete plot event. The chapter gives readers a real answer by opening on Before Shen Lan had reached the backyard, she already heard the...