I am afraid you are wrong and that source you are using is wrong on all levels. If you could provide an Arab map with the word Cajam for the Somali Indian Ocean coast then I stand corrected but you will never will be able to find it anywhere.
Ajan is a corrupted meaning for Hawiye. The root of the word Ajan is Accannæ, a Latin word. The latin writers as late as 1590 were confirming the modern name for their reference to Ajan is Hawiye.
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Its more than likely they took Arabic bearings of the Coast (Idrisi and ibn Said mention the country of Hawiye, Dimashqi goes a bit further and calls the south the coast of Hawiya named for its heat - he believed Hawiye is a misreading for Haawiyah and thought its named the area due to its hot hell bound surface).
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Above text confirms the meaning of the Latin word Accane (Ajan)
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Arabic was a lingua franca in mogadishu in several sources and mogadishu was more "Arab" than Zeila in customs and presence. Also ajam (عجم) is spelt differently to (اجان). Unless the whole region from Zeylac to Mogadishu was called Cajam, it makes no sense why only a portion of Berber land between Xamar to Bari in this context would be called Cajam.
For map evidence here is how Ajan is spelt in Arabic. Both states read as Caadil and Ajaan which shows they are both not Arabic terms but Arabised, Caadil is really Awdal here.
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In the same era, here is what Arabs called the lands of the Persians (the traditional rival of the Arabs who were the first to be called Cajam)
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Also, the Arabs since antiquity described East Africa as split between Habasha, Berbers and Zinjis. All traditionally non Arab entities. Unless the whole region was called Cajam, it makes no sense why only a portion of Berber land between Xamar to Bari in this context would be called Cajam.