Originally refers to the actual dryness of bones, implying something is as dry as it can possibly be.

Literal Use

Often used for emphasis to exaggerate the dryness of something, not always literally bone-level dry.

Exaggeration

Usually implies a negative situation, like drought or extreme thirst, which may be undesirable.

Used metaphorically, meaning a complete lack of something expected to be present.

Understanding whether 'bone dry' refers to actual dryness or lack of resources depends on the context.