I had not heard of the Seyfo before so Googled the term and found a German-language Wikipedia article to the effect that it was a genocide of Syrian Christians in WWI at the same time as the Turks’ genocide of the Armenians...but one which had remained very little known. From the map attached to the article it appears the victims were mostly in places just north of the present-day Turkish-Iraqi border and Turkish-Syrian border, but some victims were just over the border in Persia.
Yes, it was. Sorry if this article was not available in English, but you are right: it is hardly known outside the area in which it occurred. Sadly so 🙁