In Arabic, the word Amim (امیم) has two meanings: (1) one who mutters or groans due to a blow to the back of the head, and (2) one who is well-built and of good stature. (Al-Qamus Al-Waheed)
Based on the second meaning, using the name Amim is technically permissible. However, since the first meaning is also possible, and that meaning is unsuitable for a name, it is best to avoid it. Instead, one should choose a name from among the Prophets, peace be upon them, or the Sahabah, may Allah be pleased with them, or any other name with a good meaning.
The Messenger of Allah ﷺ said: Abu Al-Darda, may Allah be pleased with him, narrated that the Messenger of Allah ﷺ said: "إنَّكُمْ تُدْعَوْنَ يَوْمَ القِيامَةِ بأسْمائكُمْ وأسماءِ آبائِكُمْ فأحْسِنُوا أسْماءَكُمْ۔ (Sunan Abi Dawud, Vol. 7, p. 303, Chapter on Changing Names, Hadith: 4948, Dar Al-Risalah Al-Alamiyyah)
Meaning: On the Day of Judgment, you will be called by your names and your fathers' names, so choose good names for yourselves.
Allah the Almighty knows best.
Darul Ifta Al-Ikhlas, Karachi.