The two prostrations of forgetfulness are called the two humiliators (of Satan)

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) narrates that the Prophet (peace and blessings be upon him) named the two prostrations of forgetfulness 'al-murghimatayn' (the two that humiliate Satan).
This hadith has an authentic chain and all of its narrators are trustworthy; Abu Mujahid Abdullah bin Kaysan is among the trustworthy narrators of Marw.

Sayyiduna Abu Rafi' (may Allah be pleased with him) relates that he passed by Sayyiduna al-Hasan bin Ali (may Allah be pleased with them both) while he was praying, and he had tied the braids of his hair at the nape of his neck. Abu Rafi' undid them. Al-Hasan looked at him in anger, so he said: Turn your attention to your prayer and do not be angry, for I heard the Messenger of Allah (peace and blessings be upon him) say: "That is the seat of Satan (that is, Satan sits there)."
This hadith has a sahih (authentic) chain, and the two Shaykhs used all of its narrators as evidence except Imran. Ali bin al-Madini said of Imran bin Musa: he is Imran bin Musa bin Amr bin Sa'id bin al-As al-Qurashi, the brother of Ayyub bin Musa, and Ibn Jurayj and Ibn Ulayyah narrated from him.

Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) relates that the Prophet (peace and blessings be upon him) used to make this supplication between the two prostrations: 'Allahumma-ghfir li warhamni, wahdini wa 'afini warzuqni' (O Allah, forgive me, have mercy on me, guide me, grant me well-being and grant me provision).
This hadith has a sahih (authentic) chain, but the two Shaykhs did not record it. Kamil bin al-Ala' al-Tamimi is among those whose hadith is collected.