Why was Gulliver given the name "Quinbus Flestrin"?

During his stay in Lilliput, Gulliver is given the name "Quinbus Flestrin" by the tiny Lilliputians. According to Swift, this name means something along the lines of  "the Man-Mountain" or "the Great Man Mountain," and so it's easy to assume that the Lilliputians give Gulliver this name because he is so much larger than they are. Indeed, it's suggested that the Lilliputians are only a few inches high compared to Gulliver, and so his name illustrates his astronomical size in comparison with his minuscule hosts. Moreover, it illustrates a major theme in Gulliver's Travels: perspective. While Gulliver might seem average-sized to other humans, the vastly different perspective of the Lilliputians turns him into a "Man-Mountain" of immense size. In short, Gulliver's nickname shows how a change in perspective can drastically change the meaning of a situation, experience, or individual.