Cistern and Eyehole

Cistern noun - A sac or cavity containing fluid especially lymph or cerebrospinal fluid.

Eyehole and cistern are semantically related. In some cases you can use "Eyehole" instead a noun "Cistern".

Eyehole noun - A hole (in a door or an oven etc) through which you can peep.

Cistern and eyehole are semantically related. Sometimes you can use "Cistern" instead a noun "Eyehole".