Bro, I suppose you're giggling everytime you hear the word "Stratosphere" (aka Scrotosphere) or "Stratus" (aka Scrotus), right? :-)
"Stratum" is normal word and it's root is widely used in related words (like stratosphere), so I don't see anything wrong with this. However some people suggested that they have negative connotation to such word, so I'm not so sure now.
Edit: "stratum" is even first suggestion for synonym at
http://thesaurus.com/browse/layer . I don't see anything wrong here...