I’ve been following the discussion at the Log with great interest, and this long comment by Jongseong Park (all of whose contributions to the thread are well worth reading) is so informative I had to share it here:
The literary language in Korea was Classical Chinese until the end of the pre-Modern Era, continuing long after the invention of the Korean alphabet in the 15th century. The fact of having Classical Chinese as the literary language created a huge class of words in Korean taken from it, i.e. Sino-Korean. Even in the early 20th century, after Classical Chinese ceased to be the literary language, “neo-Sinitic” terms coined predominantly in Japan came into Korean via writing and were absorbed as Sino-Korean vocabulary.
Sino-Korean words refer specifically to those that can be written with Chinese characters and pronounced with the canonical readings of those characters in Korean, standardized through the long use of Classical Chinese as the literary language. So we exclude oral loanwords from Chinese languages past and present that differ from these canonical readings, like the older 붓 but “brush” from 筆 (canonical reading 필 pil) or the newer 쿵후 kunghu “kung fu” from 功夫 (canonical reading 공부 gongbu). We also exclude originally Sino-Korean words that have gone through sound changes to diverge from the canonical readings, like 성냥 seongnyang “matchstick” from 석류황 石硫黃 seongnyuhwang. On the other hand, we include “neo-Sinitic” words of non-Chinese (Japanese) origin like 전화 電話 jeonhwa “telephone”, and even faddish internet-age Korean neologisms like 역대급 歷代級 yeokdaegeup “historic level”.
Sino-Korean syllables are more phonotactically restricted than Korean vocabulary at large. For example, ㅃ, ㄸ don’t appear as onsets, ㅒ doesn’t appear as a medial, consonant codas are restricted to ㄱ, ㄴ, ㄹ, ㅁ, ㅂ, and ㅇ. It is often easy to tell if a word is Sino-Korean or not, especially if you recognize characters the way English speakers can recognize Latin roots like trans- or super-.
All this is to say that they are felt to be very different from more recent loanwords from English, German, or even Chinese (요우커 youkeo from 遊客 yóukè to give another example). Sino-Korean words are usually not considered 외래어 oerae-eo “loanwords” in Korean, but they’re not 고유어 goyu-eo “native words” either and form a separate, third class, 한자어 hanja-eo.
As you can imagine, the existence of these three broad categories means that there are lots of doublets or even triplets of words broadly referring to the same thing. The native and Sino-Korean vocabulary base is shared between the North and South. Yes, North Korea tends to prefer native forms more than the South, but that doesn’t mean that they have eliminated or even significantly reduced Sino-Korean words from their vocabulary. North Korean speech and texts will be peppered with Sino-Korean words to a degree comparable to their Southern counterparts. The most iconic North-Korea-related words are mostly Sino-Korean, like 주체 Juche or 로동 Rodong. Leaf through a North Korean dictionary and you will find the same preponderance of Sino-Korean words as in its Southern counterpart.
The North-South vocabulary differences are often highlighted and if you focus on those, it can give an impression that the North uses far less Sino-Korean words than the South, but I highly doubt that this is the case. The proportion of Sino-Korean words is so great that the relatively small number of divergent usage makes barely a dent. Also, Sino-Korean words also face competition in the South from native words and especially (other) loanwords.
Oh, and to clear up any misunderstanding, North Korea officially eliminated the use of Chinese characters to write Sino-Korean words from the beginning, using only the Korean alphabet to write Korean. South Korea didn’t take such a drastic measure as to forbid using Chinese characters to write Sino-Korean words, but in all the textbooks only the Korean alphabet was used to write Korean. This meant that the practice of “mixed-script” disappeared gradually and naturally as generations grew up educated only in using the Korean alphabet to write Korean—even in the most conservative South Korean newspapers the use of Chinese characters virtually disappeared by the 1990s. So after a half-century, Northern and Southern policies had the same end effect, of eliminating Chinese characters from general usage. And contrary to what one might think, North Korean students still learn Chinese characters in school, just like their Southern counterparts. So today there is negligible North-South difference on this issue, which is one of orthography, not vocabulary in any case.
Incidentally, I remember how surprised and pleased I was many years ago to learn that many Sinitic words, like 電話 “telephone,” were created in Japanese (denwa) and borrowed into Chinese (diànhuà); of course it makes perfect sense when you consider the respective curves of modernization, but we tend to take for granted the reverse order, in which Japan traditionally borrowed culture and vocabulary from China.