Typically, when referring to an image of a small object, or just something small, the prefix 'micro' is used. For instance, a tool to look at tiny objects in clear focus is a microscope. A device that takes a small sound and magnifies it is a microphone. The study of tiny living things is microbiology.
Yet when we take a photograph of something small and/or close up, we use macrofocus. This seems plainly backward to me.
This might be a stupid question, but how did this use of language develop?
You are correct that the term "macro" means large scale (e.g. macroeconomics), however its use in photography is relative to microphotography, that is imaging using microscopes.
The tradition definition of a macro lens is one that can achieve a 1:1 magnification, which means the image projected onto the recording medium is life size. So for a common APS-C camera you can fill the frame with an object about 22mm wide, but you won't be able to get any closer to the object.
A 22mm wide object is absolutely huge compared to what you would be typically looking at with a microscope, which could be hundredths of a millimetre. Hence such an image is a macrophotograph when compared to a microphotograph.
Regular photography of course regularly deals with subjects orders of magnitude larger, but there's no need to distinguish a regular "non-macro" photograph. So the name "macro" stuck and began to lose its meaning, especially when it comes to "super-macro" lenses which achieve greater than 1:1 magnification.
First definitions from dictionary.com:
microscopic: so small as to be invisible or indistinct without the use of the microscope : microscopic organisms. Compare macroscopic.
macroscopic: visible to the naked eye. Compare microscopic (def 1).
The things we photograph with macro lenses are still large enough to be seen with the naked eye (roughly cm or inch scale).
