By posting this, I now have the dubious distinction of being the author of T Nation's first article about incorrect word usage.
Man, I take no pleasure in it, but I had to do it. Let me take off my reading glasses, loosen my bun, shush some people who aren't whispering, and explain why.
Every week, noted strength coaches, some with physical therapy degrees or even PhDs in some muscle-physiology related field – guys who ought to know better – send in articles where they explain how to train a bicep or a tricep.
Fine, but just as there are no grumpkins or snarks, there are no such words – or at least no such legitimate words – as bicep and tricep. What these word-usage miscreants are trying to refer to, of course, are the biceps or triceps.
These terms originated in the 1600s and they're borrowed from Latin in which these nouns, despite the "s" at the end, are both singular. (Much like the word forceps.)
So whether someone's writing about training their left or right forearm flexors independently or together at the same time, they need to use the word biceps – with the s – regardless of the situation.
Maybe it seems trivial, but good God, when you work in a field or you're just passionate about the subject matter – in this case, weight training – you ought to know and use the correct terminology.
You don't hear many nuclear scientists saying noocular instead of nuclear. You don't hear many history professors saying Magellan circumcised the world with a 50-foot clipper (thank you, Norm Crosby).
Incorrect usage of terms intrinsic to your profession likely diminishes any respect you might otherwise command. In other words, you sound like a moron (from the Latin moros, for foolish).
So What the Hell Do These Words Even Mean?
The "ceps" in biceps and triceps, along with the word quadriceps, comes from the Latin word for head. The "bi" in front of "ceps" of course means "two-headed," so the term "biceps brachii" refers to the two-headed muscle of the brachii, or arm, and triceps brachii refers to the three-headed muscle of the arm.
Oddly enough, for some reason, the quadriceps somehow escaped this weird grammatical transmutation where the "s" got dropped when attempting to refer to the muscle in singular form. To wit, no one says they have to go train their quadricep.
Incidentally, the biceps brachii is the muscle that gave birth to the word muscle itself. It's from the Latin musculus, or "little mouse," because a flexed biceps apparently resembles the back of a mouse.
'Nuff said. My Spidey sense is telling me that Doc Ock is getting ready to dump a couple of tons of "I don't give a fucks" on my head, so let's stop now and just agree to give biceps and triceps the same courtesy we do to the quadriceps and retain their singular form in speech and in written form.