Anyone who has ever watched The Lord of the Rings has probably noticed the special intonation with which Sam says "Mr. Frodo." Some considered it a cute habit, others, an echo of good manners. But millions of viewers are still wondering: why does he say that? Why is there always this almost imperceptible, but noticeable distance between them? And why does Frodo himself never call him anything other than just Sam?
The answer is rooted in the structure of Shire society, where, despite all the pastoral idyll, social boundaries were quite clear. Sam is the son of a gardener, and he himself works as a gardener for the Bagginses. His father, Hamfast Gamgee, or simply Old Man Gamgee, served Bilbo, and then Sam followed in his footsteps. Frodo is not just a friend to him, but a master. Even when they walked side by side through Mordor, when they saved each other's lives and shared the last crumb of lembas, Sam never crossed that line.
Sam says "Mr. Frodo" not because he is afraid of being familiar, but because he truly respects him. Not for his titles, not for his wealth, but for who he has become for him, a light on the darkest road, a friend and a goal. And there is nothing humiliating in this respect. It is sincere, warm, almost brotherly.

But Frodo calls him simply Sam, because he sees him not as a servant, but as an equal. And this is perhaps where the true depth of their relationship lies. Sam sees Frodo as a master, and Frodo as a support in Sam. It is a union where each gives the other what he lacks.
This nuance in speech is a mirror of the inner world of the heroes. While others fight for the ring, power or memory, Sam simply carries his friend on his back. And he calls him "Mr. Frodo" even in the most terrible moments, because respect is something he carries no less than the ring.