Copperplate is a very neat, regular, looping handwriting, with the letters all joined in a set style. People used it a lot in the past, especially when they wanted writing to look as clear as print — invitations, ledgers, school copy-books. Few people write this way now, so the word often feels old-fashioned and a little admiring: “Look at that copperplate.” The name is copper + plate. In the 1660s a copper plate was the metal sheet you cut words or a picture into for printing. By 1817 copperplate could mean the printed page itself. From the 1820s it also meant this especially clear handwriting, which copied that printed look. So the hand is named after the print, not the other way around. There is a later verb too (copperplated), but the sense here is the writing style.

銅版體（舊式又圓又連在一起的工整英文手寫）