Full Idea
The notion of an abstract object comes from the notion of abstraction; it is in origin an epistemological rather than an ontological category.
Gist of Idea
The idea of abstract objects is not ontological; it comes from the epistemological idea of abstraction
Source
Alvin Plantinga (Why Propositions cannot be concrete [1993], p.232)
Book Reference
Plantinga,Alvin: 'Essays in the Metaphysics of Modality' [OUP 2003], p.232
A Reaction
Etymology doesn't prove anything. However, if you define abstract objects as not existing in space or time, you must recognise that this may only be because that is how humans imaginatively created them in the first place.