"Pergola Wingsproggle" was the name of a minor character in one of Betty MacDonald's Mrs. Piggle-Wiggle stories ("The Crybaby Cure") and for the 20 years since I first read those books I assumed "pergola" was just an amusing word McDonald made up for a name.
Until I read the email from A.Word.A.Day one day in July 2003 and found it definted as "an arbor formed of columns supporting trelliswork on which climbing plants are often trained." It derives from the Latin "pergula" which means a projecting roof. The URL given there for pictures of a pergola (http://www.prparchitects.com/hanoverave3.html) shows a patio which instead of being covered by a standard roof projecting from the house, has criss-cross beams supported by posts set in the ground. Various other web pages with plans and pictures of pergolas show structures that range from the house add-ons to freestanding archways -- all that they have in common is that they have open spaces for vines to grow through, and one site defines a pergola as simply "a wooden frame that gives support to climbing plants."
Pergola is also a small city near the eastern coast of central Italy, founded in the 13th century. It has some beautiful medieval churches and is a source of "a heavily perfumed purple wine made with red vernaccia grapes and sold either as Vernaculum or Vernacolo." In 1946, several gilded bronze statues, two of women and two of men on horseback, collectively known as the Bronzi Dorati, were discovered buried in a Pergola field. They have been dated to the first century AD and are the only gilded bronzes from that era still extant, but there are several theories as to who they depict.
Sources:
http://wordsmith.org/awad/archives/0703
http://dictionary.reference.com/search?q=pergola
http://www.prparchitects.com/hanoverave3.html
http://www.strohalm.nl/english/pergola.html
http://www.wrcla.org/cedarprojects/arbors/cedarpergola.asp
http://www.growinglifestyle.com/h/garden/pergola/index.html
http://www.le-marche.com/Marche/html/pergola.htm
http://www.bronzidorati.com/