pale, picket fence, limits, come to an end
埓 centers on a boundary or enclosure made of stakes: a picket fence or pale that marks limits. The idea of coming to an end extends naturally from reaching a boundary.
埓 combines 土 (earth) with a phonetic component that also suggests enclosure. The exact historical development of the right side is uncertain, but the character is associated with earthen boundaries or fences.
The left side 土 is earth, and the right side looks like a hand 爫 holding a measuring tool 寸 with a small stake 丿. Picture building an earthen fence by driving stakes into the ground to mark the limits.
For レツ, imagine a row of pickets that looks like a line of letters: L-E-T-S, but pronounced 'lets' as in 'lets you go no further'. The fence lets you go only so far: lets -> レツ.
licentious; profligate; dissipated; riotous; wild