This is from the preface to Nathan Bailey’s Universal Etymological Dictionary of 1721:
Some have remark’d that there is a constant Resemblance between the Genius of each People and the Language which they speak, and thence
The French who are a People of great Vivacity have a Language that runs extreme Lively and Brisk, and the Italians who succeeded the Romans have quite lost the Augustness and Nervousness of the Latin and sunk into Softness and Effeminacy, as well in their Language as their Manners.
The Spaniards, whose distinguishing Character is a haughty Air, have a Language resembling their Qualities, yet not without Delicacy and Sweetness.
The Romans who seem’d to be a People design’d for Command, us’d a Language that was noble, august and nervous.
The Greeks who were a polite but voluptuous People, us’d a Language exactly adapted thereto.
The English who are naturally Blunt, thoughtful and of few Words, use a Language that is very short, concise and sententious.
Quite aside from the truth of all this, it’s strange to see how the word nervous has changed in meaning. Nerves were once identified with the sinews. So nervous was a synonym for sinewy, and meant tough.
Similarly, sententious was once a word of praise. A sentence used to be an opinion or judgement (which sort of survives, in that a trial ends up with a judge giving a sentence). From that you got the idea that a single opinion could be expressed in a sentence, hence a grammatical sentence. So, if your speech is not vapid and meaningless, if it contains a thought, it is sententious.