There are multiple origins and meanings for the name Ahad:
1. Arabic forbidden name (الأحد) meaning - "Only, One, Just".
One of the names of God in Islam, along with the names of: Allah, Rabb, Rahim, Rahman, Salam, Khaliq and Hayy. Prohibited name for child, may only be used as a name-giving component.
2. Hebrew given name (אחד) meaning - "one".