jǐng
=
ji
+
(e)ng3:
a well / CL:口[kou3] / neat / orderly
Mnemonic
Joan of Arc (ji) is digging a well (井) inside the engine ((e)ng3). At first she was doing it by hand, but then she hooked up a capacitor (二) to a banana (丿) and a dinosaur bone (丨), which dig for her using the electrical energy.