Articulacy is a matter of training

Yes. Articulacy is a rather British term that I happen to like quite a lot (Americans are partial to articulateness). Articulacy can be defined as "the quality of expressing oneself readily, clearly and effectively". More often than not, it requires that a speaker be quick-witted and accurate, even under pressure. Not an easy thing. So, how does one develop the skills that are necessary to speak in such a manner? By training. Indeed. Practice does make perfect. Only by getting accustomed to using a wide range of words does one ultimately incorporate them into their own idiolect. Remember the word gap? You may say what you will about its conclusion, but the fact is that a child who is customarily exposed to a rich variety of words will obviously acquire most of them.

John Bercow (the protagonist of the video) is an admirable example of that effortless ability that every language learner ought to aspire to. Of course, one of the reasons why a speaker can be so surgically precise has to do with the sheer range of verbal options that any given thought in his/her head may conjure up. It's because of this that John Bercow can afford to be witty, severe, tactful, poetic or, if need be, even condescending. An intermediate student, however, is clearly in a different verbal universe. Let's say that you feel like eating something. What are your options? "I'm hungry" is probably high on your list. Fair enough. What else can you say?

If one can choose among different degrees of intensity, as in the sequence: peckish, hungry, starving then we are in whole different ballgame. You  realize that you may prefer to use famished and ravenous, which mean the same as starving but happen to be less frequently used and, therefore, may sound more formal. Speaking of unusual, how about the adjective esurient? And what about making use of idioms? Would you rather go for expressions like I could eat a horse, I'm hungry as a hunter or I've got the munchies... ? Remember that they all have different connotations.

Anyhow, let's turn to the video above. You will notice that Mr. Bercow says the following: 

"If the honorable gentleman doesn't trust his own exegesis of the law that's his problem, not mine, but it isn't a matter for the chair".

I simply love his use of "exegesis". Isn't it perfect? He could have chosen explanation or interpretation but opted for a term as sophisticated as exegesis, which implies the critical analysis of a cognitively demanding text (such as the constitution of a country or the Torah). Now, that is what I call... style.

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N.B. 1. Whoever edited the subtitles made one glaring mistake. The expression "in a seemly manor" should, of course, be transcribed as "in a seemly manner". Looks like haste or sloppiness  got the best of the video editor. These pesky homophones...

N.B. 2. If you happen to be obsessed with lexical options you might want to check out the famous "nose speech" from Cyrano de Bergerac.