Why is the ladybug called the 'ladybird' beetle?

The familiar beetle, usually with black spots on red, is called ladybug in the US, and ladybird in most of the rest of the English-speaking world.
The name ladybird comes from the vernacular name for the common 7-spot ladybird (Coccinella 7-puncata) in Europe: Our Lady's Bird -- the Lady in this case being The Virgin Mary. The red color of the elytra (wing cover) represents her cloak, and the seven spots represent the Virgin's seven joys and seven sorrows.
Relating Ladybirds to the Virgin Mary is not unusual, in 1991 Dr. A.W. Exell published his book History of the Ladybird in which he cites 329 common names for the Ladybird from 55 countries, of which over 80 refer to the Virgin Mary and more than 50 are dedicated to God. Contrarily one Italian name is 'Galineta del Diaolo' or 'The Devils Chicken'. Other names include the Swedish Himelska nyckla or 'The Keys of Heaven' and the Cherokee 'Great Beloved Woman'.