What are "the hills" of 121:1?

The psalm doesn't say. It asks a question and answers it: "I will lift up my eyes to the hills. Where does my help come from? My help comes from the LORD, who made heaven and earth" (121:1-2). In the WEB 121:1 is a statement and then a question. Where … from is one Hebrew word, me'ayin, which Brown-Driver-Briggs gives as "whence?". The hills is heharim, the plural, with the, of a word Brown-Driver-Briggs gives as "mountain, hill, hill-country" (tap hills). Elsewhere in the Psalms the word names the LORD's own hill: "he answers me out of his holy hill" (Psalm 3:4), and "Who may ascend to the LORD’s hill?" (Psalm 24:3). Another Song of Ascents has it twice: "Those who trust in the LORD are as Mount Zion" and "As the mountains surround Jerusalem, so the LORD surrounds his people" (Psalm 125:1-2). Jeremiah contrasts the hills and mountains with the LORD: "Truly help from the hills, the tumult on the mountains, is in vain. Truly the salvation of Israel is in the LORD our God" (Jeremiah 3:23). There mountains is the word of Psalm 121:1's hills, though Jeremiah's help is not the Hebrew word of Psalm 121:1-2. Readers hear the hills of 121:1 in more than one way from verses like these. The psalm itself names only where the help comes from, and these notes don't say what the hills stand for.