כָּר (Kar) - a lamb, especially one that has been fattened and well fed. It can also refer to lush pastures.
This word is found 16 times in 15 verses in the WLC Hebrew.

It is believed to refer to Judah as the ruler of the land of Moab. The phrase "ruler of the earth" could refer to YHWH God.

Some, however, understand the prophet as advising them to send a lamb for a sacrifice unto God, the ruler of the land of the Moabites, as well as of that of the Jews; or the ruler of the earth, as ארצ is commonly rendered: to him who is the God of the whole earth, as he is called, Isaiah 54:5. Of all the kingdoms of the earth, Isaiah 37:16. As if he had said, Make your peace with God, by sacrifice, for all your injuries done to him and to his people. (Benson Commentary: Isaiah 16:1-2 (BibleHub.com))

This appears to mean that the land must be brought to Israel the long way around the Salt Sea and up to Zion:

The name Sela (“a rock”) may refer either to the city so-called (better known by its Greek name of Petra), 2Kings 14:7, or to the rock-district of Edom and the confines of Moab generally. In either case the special direction implies that the presence of the invaders described in Isaiah 15 would make it impossible to send the tribute across the fords of the Jordan, and that it must accordingly be sent by the southern route, which passed through Sela and the desert country to the south of the Dead Sea (Cheyne). (Ellicott's Commentary for English Readers (BibleHub.com))