to soften hemp by boiling, thread
纑 centers on processing raw hemp into usable thread: softening it by boiling and then spinning it into thread. The two meanings are connected as steps in textile preparation.
纑 combines 糸 (thread) with 盧, which likely contributes the sound. The character is associated with softening hemp by boiling and the resulting thread.
The left side 糸 is thread. The right side 盧 looks like a complex pot over a fire. Picture boiling hemp in a pot to soften it, then spinning the softened fibers into thread.
For ロ, imagine a row of hemp stalks being boiled in a row of pots: row -> ロ, and the boiling softens the hemp for thread.