Answer:
Experts are of the opinion that some or all of the inhabitants of Nepal in the ancient period were likely called 'Nepals', which meant that the word 'Nepal' was used to refer to both the land and its population. These Nepals are considered the progenitors of modern-day Newars.
I believe the correct term to fill in the blank would be rumination. Trey is engaging in a practice of rumination. It is a deep or focused thinking of one that has undergone distress. It is analogous with depression and anxiety. When one is ruminating, he keeps thinking of a certain thought repetitively without thinking of any solutions to that problem.