Hadith scholars and philologists produced independent reference works to explain unfamiliar words. Abū ʿUbayd al-Qāsim ibn Sallām wrote an influential work entitled *Gharīb al-Ḥadīth*, originally not arranged alphabetically. Muwaffaq al-Dīn Ibn Qudāmah later organized its material by letters.
Abū ʿUbayd al-Harawī also contributed an important work. Abū Mūsā al-Madīnī followed earlier compilations with critical additions and supplementary material.
The purpose of these works is more than replacing an old word with a modern synonym. They explain language that becomes difficult through rare usage, historical context, or specialized senses. Establishing the linguistic meaning is an initial step toward a sound interpretation of the report.