"Peter Lassen was born on October 31, 1800 in Farum, Denmark. At the time Farum was a small village about 15 miles northwest of Copenhagen. Peter was a son of humble parents. His mother was Johanne Sophie Westergaard and his father was Lars Nielson. In the church records Lars Nielson was called farm laborer, day laborer or smallholder.
"As it will be seen, Peter's family name was not Lassen. His father was called Lars Nielson - and it was in honor of him that Peter was called Peter Larson. Larson means son of Lars. At that time it was quite common among Danish farmers that the children had their family name in honor of their father's first name. This is called patronynicon - and this alteration of family names from generation to generation makes Danish genealogical studies almost impossible. Anyway, Peter was the son of Lars and therefore he was called Peter Larson.
"While living in Denmark he spelled his name in different ways. In the beginning he was just Peter Larson. Later on, he spelled his name Peter Larssen. At other times he called himself Peter Larson Farum. In the passport records of Copenhagen from 1830, one of the public officers has simply registered him as P.L. Farum.
"That Lassen himself preferred to be called Peter Larsen Farum, when he was living in Copenhagen, must have been meant as a help for the authorities. Peter Larson was a common name in Copenhagen in these years - and it is obvious that Lassen would not like to be confused with another person.
"In America Peter Larson changed his name one more time. From then on he was Peter Lassen?"
From "Uncle Peter," page 10