甲骨文Oracle Bone Script:
金文 Bronze Character:
小篆 Seal Character:
形声字。从示，且( jǔ )声。“示”是汉字的一个部首，其义多与祭祀、礼仪有关。
示 is a Phonetic Compound, formed from a semantic indicator of 示 (a very frequently used left radical, 礻, in Chinese characters, usually indicating some connection with sacrificial rites, or a practice of offering sacrifice to gods or ancestors.), and a phonetic component of 且 (originally pronounced as jǔ not zǔ due to the years of evolution of Chinese phonetics).
祖庙 ancestral temple of a ruling house
Lily explains 祖 like this:
祖 used to be written as "且" in Oracle Bone and Bronze Inscriptions, looking like a male reproductive organ, a penis. It indicates phallism of the ancient Chinese, for they once regarded male genitals as an embodiment of generative power. In the later Shang and Zhou Dynasty, the custom of ancestor worship had gradually come into being, so "示" was added onto the character of "且", and "祖" (礻+ 且) means that the ancestors enjoy sacrificial offerings from their descendants. And 祖 originally meant an ancestral temple or shrine of a ruling house, where the sacrificial rites usually took place. In modern Chinese, 祖 usually means grandfather (祖父 zǔ fù) or ancestor (远祖 yuǎn zǔ).