Naver lists “서바나” as a translation of Spain. Is this used at all in modern Korean? Is it archaic or frowned upon compared to “스페인”?
In modern Korean, "서바나" is barely used. It seems that most of younger Korean cannot notice what "서바나" is, whereas most of them know what and where "스페인" is.
It's kind of an attempt to write non-korean word(especially the name of nation) in chinese character(한자) when Korea is unfamiliar with the Latin. And, not important, but it would be "서반아(西班牙)", rather than "서바나".
서반아 as Spain is rarely used, but 서반아어(Spanish language) is still fairly used; Especially in academic with a short form - 서어. SNU's Hispanic Language and Literature Department is 서어서문학과 in Korean, since most of universities changed their department's name to 스페인어학과.
It's like nobody calls France as 불란서 in these days, but 불어(french language/불란서어, 프랑스어) is still used.