I understand your confusment. It's based on etymological mechanism which is the same as in these words:
Hříbě - child horse (hřebec)
Kuře - child chicken (Kur)
House - child goose (huse)
Děvče - child woman (děva in old Czech)
All those are neuters...
Learning Czech was making quite a bit of noun/adjective agreement sense until: děvče = neuter. I have visions of the German nightmare of learning the memorization of der/die/das and that das Mädchen = the girl is also neuter. Wazzup wit dat?