The English term "letterbox" matches the Finnish term "postilaatikko"

Finnish Dates Back 4000 years
The oldest known piece of Finnish writing is from the 1200s. It was found in Novgorod, which is now in Russia. It’s not easy to interpret into Modern Finnish but it’s believed to be some type of spell.
The Finnish Alphabet isn’t Finnish
The Finnish alphabet has 29 letters in it. It uses the Roman alphabet as well as Swedish letters like ‘Å’, Ä’, and ‘Ö'. But some letters like ‘W’ are never used unless spelling foreign names or words.
One Author Made Finnish Lit
Aleksis Kivi wrote the first novel in Finnish called Seven Brothers. Up until the Finnish publication in 1870, all books were published in Swedish.