困
=
囗
+
木
:
New mnemonic symbol to avoid confusion with 夗: sleeping pills.
Karl Koala (ku) prepared a nest made out of Christmas trees (木) stuffed into a plastic enclosure (囗) in the encampment's bathroom ((e)n4). To make sure that he sleeps (困) really well he pops sleeping pills (困) before laying down in his nest.