Tedlock points out that cha’j is used for the game ball in Xib’alb’a while kik’ -- which also means "blood" or "resin" -- refers only to the ball of Juajpu and Xb’alanke.
Perhaps this wordplay solidifies a semantic connection for the Maya, allowing kik to refer to balls and, more distantly, to humans’ interaction with the supernatural through sacrifice or ball game challenges.
The ball in Xib’alb’a further differs from a normal ball in that it appears to the boys to be a skull. It was previously described as being coated with crushed bone; Tedlock says that what is played off as “mere decoration” by the Lords is actually a fundamental and sinister difference. Reference to this bone-ball as kik’, the word for “ball” easily associated with blood and death, seems fitting for this particular object despite the more customary use of cha’j for Xibalban game balls.
Ch'aj, the more generic word for ball, is reserved for reference to balls used by the Lords of Xib'alb'a. Considering the connection between the kik' and sacrifice, perhaps cha'j are used by Xib'alb'ans because there is no need for them to establish a connection with the supernatural -- they are the supernatural. The distinction bewteen cha'j and kik' further supports the idea that rubber and the ballgame represent the other mode of reaching the divine: blood and sacrifice.