This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
膢 is a rare character combining ⺼ (meat/flesh) with 婁, which likely contributes the sound. The exact historical development is uncertain.
The left side ⺼ suggests meat or flesh, and the right side 婁 is a complex shape. Without a clear meaning, picture a rare cut of meat labeled with an obscure character.
For ロウ, imagine a low, rare cut of meat: low -> ロウ, tying the sound to the obscure meat-related shape.