Italians have historically used the letter W as shorthand for ‘Viva’ and their road racers would be supported with banners that read “W Coppi” or “W il Giro”. The Italians also had a patriotic expression that read “Long live Italy, liberated and redeemed”, which translated to “W l’Italia liberata e redenta”… and this was further abbreviated to “Wilier”.
Thanks to John Foot and his fascinating history of Italian Cycling “Pedalare Pedalare” for binging this to my attention… also see the February 2014 issue of Cyclist for some background to the Wilier company.