This refers to Billy Tulaba, otherwise known as Tulaba, also known as Billy McLeod was a key Gippsland informant to Howitt. His name is variously spelt Toolabar, Tulabar, Talaba etc.http://adb.anu.edu.au/biography/tulaba-13226
The graph displays the other subjects mentioned on the same pages as the subject “Tulaba”. If the same subject occurs on a page with “Tulaba” more than once, it appears closer to “Tulaba” on the graph, and is colored in a darker shade. The closer a subject is to the center, the more "related" the subjects are.