Compare Psalm 90:2. What the Psalmist said of Yahweh, the teacher here asserts of Wisdom; she was before the everlasting hills.

Before the mountains were settled,.... "Plunged" (l), or fixed in the earth; and which was done by the great strength of the Lord, upon their proper bases, Psalm 65:6; and which were "aborigine", or from the beginning of the world, and therefore called the ancient mountains, Deuteronomy 33:15; to be before the mountains is a periphrasis of eternity, and is a phrase expressive of God's eternity; and being here used of the Son's, shows his eternity is the same with his Father's, Psalm 90:2;
before the hills was I brought forth; which is repeated partly to show the importance of it; this being a matter of infinite moment and concern, and deserving of the strictest attention and observation; and partly to show the certainty of it; the eternal generation of Christ being an article of faith most surely to be believed.
(l) "defixi", Montanus; "mergerentur", Tigurine version; "immersi", Vatablus, Junius & Tremellius.

settled--that is, sunk in foundations.

Instead of בּאין, in (yet) non-existence (24), we have here טרם, a subst. which signifies cutting off from that which already exists (vid., at Genesis 2:5), and then as a particle nondum or antequam, with בּ always antequam, and in Proverbs 8:26 עד־לא, so long not yet (this also originally a substantive from עדה, in the sense of progress). With הטבּעוּ (were settled) (as Job 38:6, from טבע, to impress into or upon anything, imprimere, infigere) the question is asked: wherein? Not indeed: in the depths of the earth, but as the Caraite Ahron b. Joseph answers, אל קרקע הים, in the bottom of the sea; for out of the waters they rise up, Psalm 104:8 (cf. at Genesis 1:9).