漢方薬
Aw's father was a Chinese herbology practitioner in Xiamen and a Hakka Chinese with ancestry in Yongding County. Being of a poor background, Aw first immigrated to Singapore where he stayed at the "kongsi" of his clan. He then moved to Penang and started to work as a practitioner of Traditional Chinese medicine, known as a "sinseh" () in Penang Hokkien. Afterwards, he moved to Rangoon where, with the help of his uncle, founded his apothecary named Eng Aun Tong () in 1870.