In compounds, the last element may assert what would be the ending used with it. [...] The hierarchy of rules can be overridden by what may be called re-evaluation. The expected ending is not used if there is a gain in used the other ending. [...] Re-evaluation may also help bring about a stylistic differentiation. By choosing the other ending, the speaker signals his positive or his negative assessment of the word in the particular context.
- Poldauf (2004), a pag.7