Goosefraba,
My apologies, I completely mistook your question as an abstract query about the root of the -ine suffix rather than as a specific question... me going off on a tangent again!
In strictly general terms the -ine suffix is most commonly associated with elemental halogens and -ide with their common salts (halides). What the question that you were set is perhaps trying to get at is that in that the hydroxide and cyanide species could be considered as exceptions as they are non-halides with the -ide suffix. However halides cannot really claim the -ide suffix as their own, evinced by such species as hydroxides, cyanides, phosphides, hydrides, sulphides, arsenides and carbides to name but a few!
I hope this hasn't confused things even more...
Regards
R