Cimi is the Yucatec name and Kame the K'iche', both built on the Mayan root for death, and the Classic glyph is a skull or a percentage-like sign read as death. The K'iche' Kame is also the name of one of the lords of Xibalba in the Popol Vuh, where One Death and Seven Death rule the underworld, so the day name and the mythological name are the same word.
Sixth position in the central Mexican count is Miquiztli, death, another exact agreement. In both traditions the sign is read less as an omen of dying than as the pivot between states, the point at which one thing gives way to another, and daykeepers today speak of it in connection with the ancestors and with debts owed to them.
The atlas records these as the meanings the tradition carries, not as guidance for choosing a day, which in living practice is the work of a trained ajq'ij and not of a book. Structurally, Cimi opens a trecena once in each round and is not among the four Year Bearers of either the Classic system, Ik, Manik, Eb and Kaban, or the Postclassic Yucatec system, Kan, Muluc, Ix and Kawak.
One further structural point belongs here, because the sixth position makes it visible. A day sign recurs every twenty days regardless of its number, and a numbered sign such as 6 Cimi recurs only every 260 days, so the day and the named day are two different periodicities running at once. Everything the count is used for depends on that difference.