Jamieson, Fausset and Brown on Isaiah 36:2

2. Rab-shakeh--In 2Ki 18:17, Tartan and Rab-saris are joined with him. Rab-shakeh was probably the chief leader; Rab is a title of authority, "chief-cup-bearer."

Lachish--a frontier town southwest of Jerusalem, in Judah; represented as a great fortified city in a hilly and fruitful country in the Koyunjik bas-reliefs, now in the British Museum; also, its name is found on a slab over a figure of Sennacherib on his throne.

upper pool--the side on which the Assyrians would approach Jerusalem coming from the southwest (see on Is 7:3).