Why do loanwords tend to be more polite, formal, technical, etc. than native words? I've noticed that native words in my language, especially those that refer to body waste and genitals, tend to be more informal, and even more vulgar than loanwords. The same goes with English: d__k and c_ck are vulgar, excrement is acceptable, feces is formal; lip is common and labia is technical. Why is that?
There are various reasons, including:
Scholarship is often done in other languages before it's done in local languages. In Western Europe, for many centuries scholars exchanged technical knowledge in Latin, so it was natural to borrow words from Latin for technical senses when they started talking about these topics in their own language.
Even though not many people learn Latin anymore, the habit has been formed, and we tend to think of Latin / Greek words as more technical than Anglo-Saxon words. This was the same case in Korea and Japan, which used Chinese as the language of learning.
When words are borrowed, their "raw" meaning and all of its associations are less prominent. Once a word has vulgar connotations, it's hard to remove these connotations, and so people often seek a "nicer" alternative. Words recently borrowed haven't had the time to build up the vulgar connotations, and the meaning is less vivid, too. So a loanword tends to be used in more formal or polite situations, when the native word is felt to be too vulgar. This formality is reinforced by its use - we hear a word like "feces" used only in formal situations, so we think of it as formal, and it gains that connotation, which may make it more resistant to gaining vulgar connotations later.