Celtic sailing arriving June 1881

I found my great grandfather Hans Myhre in the database at Castle Garden or at least I think it is him. He was born 6/18/1861 and this Hans Myhre shows he is 20 which means he was born in 1861. Since this ship sailed from Liverpool, how did he arrive there? I cannot seem to locate him in any immigrant database sailing from Norway. Any help would be appreciated. Thanks, Cheryl Akers