I've seen the honorific "o"/"go" (is it called bikago?) being used as politness or reverence: o-cha for non-western tea, o-namae when talking about someone else's name, o-genki instead of just genki, and o-tera for Buddhist temple.
However, I've recently come across (in "Welcome to Japanese") o-tearai for bathroom, which is presumably a modification of tearai.
Google-sensei directed me to http://www.learnjapanese.com/japanese-o-factor/ and http://www.peterpayne.net/2008/05/useful-japanese-honorific-o.html , which talk about it being used for dirty things, such as a potty, diapers and female anatomy.
Is it sometimes used to soften things that are somehow "dirty", or is it being used ironically?