Where did you get the Japanese term for Swamp Kobold Trooper? Did you look at the Japanese novel or did you use Google or something of the sort? Because I took a look at the chapter that you referenced and saw that the term was スワンプコボルド・トラッパー, rather than 沼コボルド・トラッパー. Practically all monster official names in SAO are supposed to be in English, so the term is most likely going to be entirely in katakana. The fact that you used kanji makes me think that you just tried translating the English name to Japanese and got the actual Japanese equivalent for swamp.
For future reference, inserting false Japanese terms counts as misinformation and I have very low tolerance for that. So, if you do not have access to the Japanese raw, please contact someone who does to look up the term, but never try to guess the term yourself.