What would ‘Lamb‘ mean to the people who heard John?

To them the lamb was the symbol of sacrifice, to restore a relationship with God,  reminding them of Isaiah, Chapter 53 :

“Surely he took up our pain and bore our suffering, yet we considered him punished by God, stricken by him, and afflicted

But he was pierced for our transgressions, he was crushed for our iniquities; the punishment that brought us peace was on him, and by his wounds we are healed.

We all, like sheep, have gone astray, each of us has turned to our own way; and the Lord has laid on him the iniquity of us all.

He was oppressed and afflicted, yet he did not open his mouth; he was led like a lamb to the slaughter.”