No, personally I don't think it seems appropriate to just answer the question with an answer about the origin of the name Harem. I would imagine an answer just addressing the name may be downvoted.
A) Most importantly the question isn't about the origin of the name, it's the origin of the genre, of which the name in English (and perhaps other languages) is only a small (and perhaps insignificant) part. You seem to imply the OP has asked about the name, but I really don't see that in the question.
B) To a lesser degree, as someone who doesn't know the genre but who knows English the name appears self evident. The dictionary definition of a Harem, together with the description of the genre in the question, I can see why the label has been used.
If there is something interesting about the origin of the name, feel free to add it as additional detail to an answer you write addressing the origin of the genre. There's no reason here why multiple answers can be provided to the same question.