Wordorigins.org

The meaning behind the name Newfoundland is pretty obvious. Explorer Giovanni Cabato, a.k.a. John Cabot, called the land new founde isle in 1497. Within a few years the name Newfoundland was in use. From a 1502 quotation found in J.A. Williamson’s 1962 The Cabot Voyages:

Item to the merchauntes of bristoll that have bene in the newe founde launde.

(Sources: Dictionary of Canadian Place Names; Illustrated Dictionary of Place Names; Oxford English Dictionary, 3rd Edition)