fence, railing, enclosure
堵 centers on a physical barrier that marks a boundary or keeps things in or out: a fence, railing, or enclosure.
堵 combines 土 (earth) with 者, which likely contributes the sound. The earth radical suggests a wall or barrier made of earth, fitting the fence/enclosure meaning.
The left side is earth 土, and the right side 者 looks like a person or structure. Picture an earthen wall or fence built around a person's land to form an enclosure.
For ト, imagine a toe getting caught on a low fence: toe -> ト, and the fence is the enclosure.
relief; reassurance
fence; wall; hedge
to live in peace (of the people)
in crowds (of spectators); in great numbers
row of people lined up; forming a row; lining up (side by side)
sense of relief; feeling of relief
recognition and guarantee, by the shogunate, of ownership of the inherited estate of a samurai who pledged allegiance to it (in the Kamakura and early Muromachi periods)