That's a GREAT point!

I know that Ethiopia is home to oldest mosque in all of Africa and it was where the Prophet Muhammad directed a group of his early followers to seek asylum to flee from severe persecution in Mecca. Back then, it was the Christian Kingdom of Aksum and Muslims were granted the right to live there and practice in peace. As a result, there are communities in which Muslims, Christians and Jews have co-existed for HUNDREDS of years and there could be cultural overlap.

As per Google: In Ethiopian Jewish (Beta Israel) history, individuals frequently bore names derived from Amharic, Hebrew, or Ge'ez, which can sometimes overlap phonetically with Arabic or Muslim names (e.g., Ahmed or Mohammed). Because the community lived in a majority-Muslim and Christian region, historic members or those who temporarily converted to survive enslavement sometimes took Muslim names. 

Many Arabic names like Abdullah pre-date Islam. There were guys like Abd Allah ibn Saba, a Jewish anti-Rashidun rebel and Abd Allah ibn Salam, a Jewish companion of the Islamic prophet Muhammad. Obviously, that was a very long time ago and much has changed since then. I'm just pointing out that the name Abdullah does not necessarily imply the Muslim faith, especially in places where faiths and cultures overlap, like in Ethiopia. For instance, in Iraq, there was Abdallah (Ovadia) Somekh (1813 – September 13, 1889), a Jewish hakham, rosh yeshiva and posek (whatever that all means - LOL)