This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 鼺 is uncertain. It combines 鼠 (mouse/rat) with 畾, but the original semantic and phonetic roles are unclear.
The left side is a mouse 鼠, and the right side 畾 looks like stacked fields. Imagine a mouse scurrying through layered fields, but its true meaning is uncertain.
For ルイ, imagine a mouse named Louie scurrying through the fields: Louie -> ルイ.