ancestor, originator

祖 is composed of the radical of 示(altar) and 且(and, yet). 示 is the pictograph of an ancestral altar, indicating sacrifice or worship, while 且 depicts a chopping board; in ancient times, the chopping board was not only used for cutting meat but also to hold sacrificial offerings, and the ancestors of previous generations were often the most important objects of sacrifice; thus 祖 refers to ancestors.