It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the most beloved names to the Prophet (peace and blessings be upon him) were Abdullah and Abdur Rahman.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 6122
Hadith Gradingحکم دارالسلام:حديث صحيح، وهذا إسناد ضعيف لضعف عبدالله العمري.