This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
橑 combines 木 (tree/wood) with 尞, which likely contributes a phonetic element. The exact historical development is uncertain.
The left side is 木 (tree/wood), and the right side 尞 looks like a complex structure. Imagine a wooden beam or rafter made from a tree, but the exact meaning is unclear.
For ロウ, picture a low wooden beam: low -> ロウ, and the wood radical 木 hints at the material.