Chicchan in Yucatec is Kan in K'iche', a name that in the highland lists means both serpent and the colour yellow. The overlap of serpent and yellow is not accidental in Mayan languages, and it is one of the reasons the fifth sign is so consistently drawn with snake imagery from the Classic inscriptions through to the divining almanacs of the Dresden Codex.
The tonalpohualli agrees exactly: fifth position in central Mexico is Coatl, serpent. Where Maya and Nahua signs match this plainly, it is usually taken as evidence that the name travelled with the count rather than being attached locally afterwards, though the direction of travel and the date of the borrowing are not settled and the earliest secure attestations of the 260-day count come from Oaxaca rather than from either the Maya lowlands or the Basin of Mexico.
Chicchan opens a trecena once in each 260-day round. It is not a Year Bearer in either the Classic set of Ik, Manik, Eb and Kaban or the Yucatec set of Kan, Muluc, Ix and Kawak, which is a structural fact about its position in the twenty rather than anything to do with its meaning: the four bearers must be spaced five apart, and Chicchan sits between two of them.
The serpent of the fifth day is not only a calendar sign. In Ch'orti' ethnography recorded in the twentieth century, chicchan beings are serpents associated with springs, rivers and the bringing of rain, and are addressed in agricultural ceremony, so the word survives in Maya religious language independently of the day count. Sign and being are the same word, and it is not clear which usage is prior.