The answer is Xi Bu Xin Nuan’s explanation: Xi means sitting; Xia means free time.

He got up before even having time to sit on the mat and get warm.

It originally meant running around and not being able to live in peace.

Later, he said he was very busy and didn't have time to sit down for a while.

From: "Huainanzi Xiuwu Xun": "Confucius has no Qian Tu, Mozi has no warm seats." Han Yu of the Tang Dynasty, "Contending Ministers": "Confucius has no time to warm the seats, but Mo Tu cannot warm Guizhou." Example: Really busy

Got it~, the man fell back on his horse.

◎Chapter 51 of Li Baojia's "The Appearance of Officialdom" in the Qing Dynasty Grammar: subject-predicate form; used as predicate, object, and complement; to describe busy affairs.