good question, as I've learned lately in being asked to explain some expressions I use and the English language in general, well, we make no sense at all really, very illogical and inconsistent
eg) after watching a dinosaur cartoon, i was asked how come there were no houses back then...i said we came later and lived in caves...that's why they were called cavemen....he asked if we were now called housemen...
i said no, not really at all, but good question...but, well, there are streetpeople, tentpeople, trailerparkpeople ...anyhow, don't think too much, we're usually just called human beings...best to just memorize that one, kiddo
rm, in this case, no difference, just a perception thing: is the half-assed full or full-assed half empty? I am the latter type
interesting link discussion:
http://www.languagehat.com/archives/002155.php
the one argues that no-assed is preferable to full-assed