Entry #3 for 13 May 1728 is this the entry for Erich with mother Malin and father Pehr Laurinpk Halonen Kotajärvi
I get confused because Pehr Laurinpk Halonen married Malin Antintytär Cotajärvi when he moved onto Cotajärvi farm and I find records with Pehr using Halonen or Kotajärvi or both.
I don't know why you are confused so I must guess - and I am probably
guessing wrong. (-:
Laurinpoika - patronymic name
Halonen - surname
Kotajärvi - toponymic name
You seem to think that the names in sources are the names our
ancestors used. Since common people (dreng, piga, bonde, torpare,
inhys) had no need to write their names we don't know the names they
used. We only know the names used by Swedish authorities in Swedish
Finland and Russian authorities in Russian Finland. (From 1721 to 1809
there were two Finlands, one in Sweden and one in Russia. Neither one
or both together was the same area than Finland nowdays.)
a) You have read a name in one source.
b) You have read another name in another source.
c) You have drawn a conclusion that the names refer to the same person.
d) You are wondering why the names are different?
Well, they just are different. I have been "doing genealogy" for so
many years that I do not think any more why people in different times
and places did the things differently than I would do.