John Gill Commentary 2 Chronicles 32:18

"And they cried with a loud voice in the Jews` language unto the people of Jerusalem that were on the wall, to affright them, and to trouble them; that they might take the city." — 2 Chronicles 32:18 (ASV)

Then they cried with a loud voice in the Jews' speech to the
people of Jerusalem that were on the wall
The messengers of Sennacherib, particularly Rabshakeh the chief speaker; though they were desired to speak in the Syrian language, (Isaiah 36:11Isaiah 36:13),

but this they did to affright them, and to trouble them, that they
might take the city. They did this to throw them into terror and confusion, that they might prevail upon them to deliver up the city to them.