Iao (or I-ha-ho)
A mystic emblem said by Clement of Alexandria (ca. 150–ca.
213 C.E.) to have been worn by the initiates of the mysteries of
Serapis. It was said to embody the symbols of the two generative
principles, and is thus similar to aum in India. Serapis was an
Egyptian divinity who, with Isis, supplanted Osiris and Apis
and acquired their attributes. As a healing divinity, Serapis was
a rival of Aesculapius in Rome and in vogue in the Greek cult
of Asklepios at Pergamon and Alexandria.