Well, it's fairly obvious that goji shouldn't be classed as a common word: two out of the four forumites who've commented have never heard of the word. Also, the Merriam-Webster identifies it as a less common alternative to goji berry. And my spell checker underlines it.
It seems the word first appeared in English in its present form around 2002, derived from the Chinese gouqi. According to Wiktionary it was a "marketing coinage".
It will be accepted in future as a rare word.