John Gill Commentary Mark 5:11

"Now there was there on the mountain side a great herd of swine feeding." — Mark 5:11 (ASV)

Now there was there, nigh unto the mountains
Where this man often was, (Mark 5:5) according to Beza, the mountains of Galaad, which ran through that country, or the mountains that surrounded Tiberias. Some copies, as the Alexandrian copy and others, read "at", or "about the mountain", in the singular number. The Vulgate Latin and Arabic versions read, "about the mountain". The Syriac and Ethiopic, "at the mountain"; so in (Luke 8:32) ,

a great herd of swine feeding ;
on one side of the mountain, or mountains; it may be called a great one, for there were about two thousand hogs in it.