Inherited from Ottoman Turkish صمیمیت (ṣamimiyyet), from Arabic صَمِيمِيَّة (ṣamīmiyya, “cordiality, intimacy”), from صَمِيم (ṣamīm, “essence, core”) + ـِيَّة (-iyya, nisba suffix).
Practice speaking and memorizing "samimiyet" and many other words and sentences in Turkish.