Interesting that this should come up. I was looking through one of Chas. Funk's books on word and phrase origins, when I noticed that muscle and mussel are both from Latin musculus 'little mouse'. The related Sanskrit mushka 'testicle, female pudendum' (Hode and weibliche Scham in Pokorny); I wonder why A-H dropped the second from their review of English words derived from the root *mu:s- 'mouse; muscle'. Another cognate is Old Bulgarian (aka Old Church Slavonic) mush'tsa 'brachion, arm' and Greek muschon 'sex organ' (Geschlechtsorgan in Pokorny, to andreion kai gunaikeion morion 'the masculine and feminine genitals' in Liddell-Scott). Something about mice and body parts in PIE.

http://www.bartleby.com/61/roots/IE332.html