Talk:Bomb/@comment-121.208.111.171-20151011112540/@comment-86.3.162.198-20151209035311

'o' is an honorific adding respect to the person you are addressing

'nii' is derived from 'ani' meaning older brother'

'-chan' is an honorific denoting affection, and can also be used to show past relations with someone, generally used more when referring to girls but not 'weird' to be used with a boy (although '-kun' is used more with boys, however I don't think that is used much, if at all, with familial pronouns such as 'nii', 'jii', 'nee' as well as others)

all together it forms 'onii-chan', showing Bang wishes to show respect for his brother, acknowledge him as his older brother, and show affection and love towards his brother.