What is the meaning of ごおん?

呉音: One category of on'yomi (音読み, おんよみ), the Japanese approximation of the original Chinese pronunciation of a kanji character.

五陰: Alternate for 五蘊 (goun): skandha, any of the five types of attribute that constitute the personality of an individual.

五音: Alternate reading for 五音 (goin): the five basic musical tones in the Wu Xing Taoist tradition.

御恩: A favor received from someone; a reward one receives or gives to someone else.

語音: The sound or pronunciation of a word; a phoneme.

Source: wiktionary.org