"-ish" is usually added to a word to indicate "like", "kind of" or "similar to". Eg. heavy-ish = kind of heavy (but not definitely - you can carry it) I'm not sure about "diddy-ish" (kind of like 'diddy'?), but it seems "neddish" might relate to being "ned-like": http://en.wikipedia.org/wiki/Ned_(Scottish) "Ned" is not a commonly-known term.

No idea.