This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The historical origin of 臰 is uncertain. It visually combines 自 (self/nose) and 死 (death), but the intended meaning and development are unclear.
With 自 (nose) over 死 (death), imagine a smell so bad it could kill: a deadly stench. This ties to the kun readings くさ.い (stinky) and にお.う (to smell).
For シュウ, picture a shoe that smells so bad it could kill: shoe -> シュウ, and the deadly stench rises from the shoe.