亶
=
亠
+
回
+
旦
:
Mnemonic symbol: to bow and show how earnest you mean it.
Don Quixote (d) ordered a beer at the bar in the anthill (an3). The barkeeper questions whether or not Don Quixote will return (回) the mug (旦) after he finishes his beer, so Don Quixote bows and shows how sincere (亶) he is by handing over his beret (亠) as security deposit.
Maud Younger used to wear a monk's cowl when leaving the space station, but when she got a royal ermine coat she gladly threw the monk's cowl out. Nowadays she uses to wave a petal leaf matching her new coat.