19 You will see those arrogant people no more, people whose speech is obscure, whose language is strange and incomprehensible.

Read Isaiah 33:19 Using Other Translations

Thou shalt not see a fierce people, a people of a deeper speech than thou canst perceive; of a stammering tongue, that thou canst not understand.
You will see no more the insolent people, the people of an obscure speech that you cannot comprehend, stammering in a tongue that you cannot understand.
You will no longer see these fierce, violent people with their strange, unknown language.