Normal modern spelling of this word, in the singular, is "bicep":
And that second number is inflated by contractions and possessive-s ("my right bicep's gonna hurt tomorrow!" or "my right bicep's circumference is 30cm").
Now, Google hits are not the highest authority on the language, but sometimes it's a good help for highlighting things that are pretty obvious anyway.
But I accept that certain authors write "biceps" for the singular. (It makes me do a double take, but it's not incorrect.) How does Wiktionary handle this? Should the content of this page be copied to bicep, so they both have the same explanations etc.? Or should the content be moved to bicep and a note left here "alternative spelling of bicep; plural of bicep"? Gronky (talk) 11:02, 20 January 2014 (UTC)