Here be mǫrsugr, mörsugur (bone marrow or fat sucker) or hrútmánuður (ram month) (see the Dictionary of Old Norse Prose). We’re in the third month of winter. The coldest month of the year that lasts roughly from end of December to end of January.
The Bókarbót text from the eleventh century mentions Ýlir and the month of Mǫrsugr. Where does the idea of fat sucking come from? That harsh cold might be a reason, sucking the fat out of any human or animal. Or, the romantic notion from the Icelandic scholar Gísli Jónsson who states that it “draws the spirit of life” (see Icelandic Almanac or Iceland Monitor).
Snorri mentions hrútmánuður in his Edda (see Icelandic Science Web). The ram month undoubtedly refers directly to husbandry, sheep farming. The problem at the moment is that most online sources only state that its called ‘ram month’ but don’t explain why. My hunch is a possible connection to the breeding season? How, that is the question that remains. Perhaps there are more scientific studies I haven’t seen yet, or perhaps even something in the Grágás, the medieval Icelandic laws? Let me know if you have any good leads on Viking Age sheep farming!