looking to trace ggf "Charles C. Erichson" born 1842 Copenhagen
I have been able to learn that my great grandfather, who was known by my ancestors as Charles E. Holmes, used the name Charles C Erichson between about 1860 when he says he immigrated from Denmark, and 1868, which is when I think he changed his name to Holmes. He reported that he and both his parents were born in Denmark - in one place he says Copenhagen. No dates, no names, nothing about siblings. I know nothing about what port he embarked from or on what ship he traveled. I have his date of birth - in 3 versions. Always 21 July, sometimes 1842, also 1844 and 1845.My best guess is 1842. I have no idea if Erichson was his true surname, and even if it was, was it a patronymic? or an actual surname? (And I'm aware that Erichson looks like a Swedish name. And FWIW, our y-DNA is N1c1, which points to a Finnish/Latvian/Siberian deep ancestry, unusual in Denmark or even Sweden, really).
With so many unknowns, and such limited information, where might I start searching for him in Denmark? Is it even feasible?
Thanks for any thoughts or suggestions you might have.