surname, constellation, to wear
娄 is a rare kanji with no clear standalone meaning in modern Japanese. Its given senses include a surname, a constellation, and the act of wearing, but these do not form a single conceptual center. Treat its meaning as uncertain and context-dependent.
The exact historical development of 娄 is uncertain. The modern form visually contains 米 and 女, but these components may not reflect the original structure.
The top 米 (rice) and bottom 女 (woman) can be combined into a scene: a woman wearing a rice-patterned garment, tying the 'to wear' sense to the visible shape. The surname and constellation meanings are harder to visualize, but the same image can serve as a placeholder.
For ル, imagine the woman in the mnemonic wearing a loose (ルーズ) garment: loose -> ル, and she ties it with a rice-patterned sash.