to respectfully inform
叝 centers on the act of respectfully informing or reporting to a superior. It is a rare, formal character with a narrow meaning.
The exact historical development of 叝 is uncertain. It appears to combine 去 with 卩 and 又, but the original semantic and phonetic roles of these components are not clearly established.
The left side 去 (go away) and the right side 卩又 (a kneeling figure with a hand) suggest a person departing after delivering a respectful report.
For コウ, imagine a court official making a respectful report with a deep bow: the bowing motion sounds like 'koh' (コウ).