If the term "external medicine" makes no sense, why the term "internal medicine"?

I guess because medicine just covers all medicine as a whole and to specify you say internal medicine? Saying just medicine automatically means external medicine? Like in sociology we use the terms sanctions which covers both positive and negative sanctions but because when talking of good sanctions we say rewards most of the time just the word “sanctions” has come to mean punishments.

It depends on how you look at the terminology as opposed to how others view it.
“External medicine” applies to the outside of the body while “internal medicine” applies to the inside of the body.

Internal medicine refers to the internal organs. There are no external organs. Other specialties deal with skeletal issues, neurological issues, cardio-pulmonary issues, cranial issues, etc.

Males have external organs.

^^^^ I stand corrected.

Internal Medicine is a specialty.

Skin is pretty external. So are wounds like cuts and scrapes. Eyes and the mouth are sort of, too.

Is it debatable what the internal organs are?
https://www.education.vic.gov.au/school/teachers/teachingresources/discipline/science/continuum/Pages/internalbody.aspx According to Google Images and different soiurces, it’s either 5, or 6, or 9 or more.

https://tinyurl.com/y3d4e8no ( internal organs, Google images)