Most translations render the symbol of God’s covenant to Noah and humanity as “rainbow,” and we all agree that’s what God was referring to, but the Hebrew word here also the word for “bow,” as in an archer’s bow. A weapon of war.
The imagery is that God has hung up the weapon.
My bow I have given in the cloud, and it hath been for a token of a covenant between Me and the earth; and it hath come to pass (in My sending a cloud over the earth) that the bow hath been seen in the cloud, and I have remembered My covenant which is between Me and you, and every living creature among all flesh, and the waters become no more a deluge to destroy all flesh; and the bow hath been in the cloud, and I have seen it — to remember the covenant age-during between God and every living creature among all flesh which [is] on the earth.’
Genesis 9:13-16 (YLT)