Musannaf Ibn Abi Shayba 26:212

Waki’ narrated to us, from Sufyan, who said: I said to al-A’mash, "Why was it named al-Akdariyyah?" He said: "Abd al-Malik ibn Marwan posed it to a man who was called al-Akdar, who used to look into the laws of inheritance (fara'id), and he made a mistake in it, so he named it al-Akdariyyah." Waki’ said: "And we used to hear, before Sufyan explained it, that it was only named al-Akdariyyah because Zayd’s opinion in it became 'kadir' (turbid/disturbed), as his opinion did not become widespread."