The word "祭坛" is formed by combining the character "祭", which historically depicts a hand offering meat over an altar to signify sacrifice or worship, with the character "坛", a simplified form meaning altar, constructed from the radical "土" (earth) and the component "云" serving as a phonetic indicator. Together, they create a compound where "祭" modifies "坛" to specify an altar used for sacrificial rituals.