Is the ḥadīth regarding the coming of the jinn to the Prophet, upon him be peace and blessings, as if they were "az-Zutt" authentic, and what is meant by it?

The hadith mentioned in the question was narrated by Imam Ahmad in "Al-Musnad," but its text (matn) and chain of narration (isnad) are debated due to its strangeness and its contradiction with what Muslim narrated from Ibn Mas'ud, who stated that he was not with the Prophet, peace and blessings be upon him, on the night of the jinn. As for its chain of narration, it includes Amr al-Bakali, whose companionship [with the Prophet] and hearing from Ibn Mas'ud have not been established.

Assuming the hadith is authentic, the word "hanin" is the plural of "han," and it is used as a كناية (figurative expression) for persons, as becomes clear from the context of the hadith which describes them as "as if they were the Zutt," meaning they resembled the well-known people of Zutt.

As for the phrase "So they came, and they began to mount the Messenger of Allah, peace and blessings be upon him," its meaning is that they crowded and gathered around him, eager to listen to the Qur'an, as stated in the Almighty's saying about the jinn: "And that when the servant of Allah stood up to invoke Him, they were about to be a dense crowd upon him" (Al-Jinn: 19).