spell, curse, malediction
咒 centers on spoken or written words intended to bring supernatural harm or control: a spell, curse, or malediction.
咒 is an older form of 呪, combining 吅 (two mouths, suggesting repeated speech) with 几 (a low table or stand), possibly evoking ritual incantation. The exact historical development is uncertain.
Two mouths 吅 chanting over a ritual stand 几: imagine a pair of sorcerers reciting a spell together to place a curse.
For ジュ, picture a jewel (ジュエル) glowing on the ritual stand as the two mouths chant the curse: jewel -> ジュ.