tower, surname
譙 centers on a tall structure used for watching or signaling: a tower. The surname meaning is a separate, unrelated use of the same character.
譙 combines 言 (speech) with 焦, which likely contributes the sound. The tower meaning may derive from a watchtower used for signaling or calling out, but the exact historical development is uncertain.
The left side 言 suggests words or calling out, and the right side 焦 looks like a bird (隹) over fire (灬). Imagine a tall tower where a lookout shouts warnings, like a bird calling from a high perch above a fire.
For ショウ, picture a show being announced from the tower: a town crier shouting 'Show! Show!' from the top. Show -> ショウ.