Chapter 16(p. 77): When listing the various kennings for Loki, he is called "Sif’s hair-harmer," referencing his malicious act of cutting her hair which sets the story in motion.
…of Sigyn, enemy of gods, Sif’s hair-harmer, maker of mischief, the cunning As, accuser and tricker of the gods, contriver of Baldr’s death, the bound one, wrangler with Heimdall and Skadi. As Ulf Uggason says here:
Chapter 32(p. 94): In a list of poetic names for gold, "Sif's hair" is explicitly mentioned as a valid kenning.
How shall gold be referred to? By calling it Ægir’s fire and Glasir’s foliage, Sif’s hair...
Chapter 34-35(p. 96): This is the main origin story. The section begins by asking why gold is called "Sif's hair" and proceeds to tell the tale of how Loki cut off her hair and, under threat from Thor, promised to have the black-elves forge a replacement.
Why is gold called Sif’s hair? Loki Laufeyiarson had done this for love of mischief: he had cut off all Sif’s hair. And when Thor found out, he caught Loki and was going to break every one of his bones until he swore that he would get black-elves to make Sif a head of hair out of gold that would grow like any other hair.
Chapter 35-36(p. 97): The story concludes when Loki presents the treasures to the gods. He gives the golden hair to Thor for Sif and describes its magical property of rooting itself to the flesh.
Then Loki gave... the head of hair which was to be Sif’s to Thor... and announced the features of all the precious things... the hair was rooted in the flesh as soon as it came on to Sif’s head...
Chapter 45-46(p. 113): In a verse from the old Lay of Biarki, a kenning for gold is used that directly references Sif's hair.
The generous lord pushed, men received, Sif’s scalp-strings...
If you find incorrect information or you know of missing references, please contact me on [email protected]