Meaning
The whole thing; not concealing the less attractive parts.

Origin
This phrase is said to derive from Oliver Cromwell's instructions to the painter Sir Peter Lely, when commissioning a portrait.

At the time of the alleged instruction, Cromwell was Lord Protector of England. Lely had been portrait artist to Charles I and, following the restoration of the monarchy in 1660, he was appointed as Charles II's Principal Painter in Ordinary.

Lely's painting style was, as was usual at the time, intended to flatter the sitter. Royalty in particular expected portraits to show them in the best possible light, if not to be outright fanciful. Lely's painting of Charles II shows what was expected of a painting of a head of state in the 17th century. It emphasizes the shapely royal calves - a prized fashion feature at that time.

From: http://www.phrases.org.uk/