The word 'spirituality' is a noun that is rooted in the adjective 'spiritual', which again is rooted in the noun 'spirit'.
A noun is a substantive because it indicates the substantivity of something. The word 'substantive', like the related word 'substance', is etymologically rooted in the Latin word 'substantia', which is composed of the prefix 'sub-', meaning 'under' and the word 'stare', meaning 'stand'.1 So a substance is under-standing. That something is under-standing means that it is a ground. For what is under-standing is underlying.
Now it is through characteristics that a substance makes itself known. To become known means to proclaim. It is through proclamation that a substance makes itself predictable. This word 'predictable' has the same etymological root as 'predicate' in the Latin 'praedicare', which is composed of the prefix 'prae-', meaning 'forth', and the word 'dicare', meaning 'acclaim'.2
So spirit as substance becomes predictable in the spiritual. Now when the predicate 'spiritual' is substantivized a postfix like '-ness' or '-ity' is added to it, resulting in words like 'spiritualness' and 'spirituality'. The referents of these words are however different. When the postfix '-ness' is added to a word the latter rather refers to a generality that has an existence on itself but in which different particularities participate, like for instance 'goodness'. This corresponds with the Platonistic thought.3 However when the postfix '-ity' is added to a word the latter rather refers to a generality that has been brought about by humans, like for instance 'Christianity'. This corresponds with the Aristotelian thought.4 The aforementioned is valid at least for 'spiritualness' and 'spirituality'. 'Spiritualness' refers to the by itself existing generality of being spiritual while 'spirituality' refers to the by humans brought about generality of being spiritual.
Spirituality is the human effort to become spiritual.