What is "heimdalargaldr"

Heimdalargaldr ( Old Norse " Heimdallr's galdr") is an Old Norse poem about the god Heimdallr of Norse mythology. The poem is mentioned in two books of the 13th century Prose Edda book— Gylfaginning and Skáldskaparmál—but outside of a single, two-lined fragment that appears in Gylfaginning, the poem is considered to be lost. In the surviving fragment, Heimdallr comments that he is the son of nine sisters (the Nine Mothers of Heimdallr). Scholars have commented on the information the surviving lines presents and have speculated about what the poem may have contained.