话说唐朝时期，有个才华横溢的官员，名叫李白。一天，他正与友人饮酒作乐，突然听到窗外传来一阵阵奇怪的叫声。好奇之下，他推开窗户，只见一只肥胖的猫正倒挂在树枝上，拼命地挣扎着，模样滑稽至极。李白和友人见状，都忍不住哈哈大笑，笑声震彻庭院。李白的友人指着那只猫说道：‘这猫就像那舞台上的小丑，真是滑稽可笑！’李白听了，也觉得好笑，说道：‘是啊，我真是忍俊不禁啊！’说完，两人又大笑起来，笑声久久不息。这便是‘忍俊不禁’的由来。此后，‘忍俊不禁’便成了人们形容忍不住要发笑时常用的词语，表达了那种发自内心的愉悦和轻松。
huashuo tang chao shiqi, you ge caihua hengyi de guan yuan, ming jiao li bai. yitian, ta zheng yu you ren yinjiu zuole, turan ting dao chuang wai chuan lai yizhenzhen qiguai de jiaosheng. haoqizhixia, ta tuikai chuang hu, zhijian yizhi feipang de mao zheng daogua zai shuzhi shang, pipeng di zhengzhazhe, muyang huaji zhiji. li bai he you ren jian zheng, dou renbuzhu haha da xiao, xiaosheng zhenche tingyuan. li bai de you ren zhi zhe na zhi mao shuo dao: ‘zhe mao jiu xiang na wutai shang de xiao chou, zhen shi huaji kexiao! ’ li bai ting le, ye jue de hao xiao, shuo dao: ‘shi a, wo zhen shi renjunbujin a! ’ shuo wan, liang ren you da xiao qilai, xiaosheng jiujiu buxi. zhe bian shi ‘renjunbujin’ de youlai. ci hou, ‘renjunbujin’ bian cheng le renmen xingrong renbuzhu yao faxiao shi changyong de ciyu, biaoda le na zhong fa zi neixin de yuyue he qingsong.