Ambrose Philips (1671-1749). His nickname was bestowed upon him by Harry Carey, the dramatist, for his verses addressed to Lord Carteret's children, and was adopted by Pope. This was not John Philips, author of the Splendid Shilling. “Namby” is a baby way of pronouncing Ambrose, and “Pamby” is a jingling reduplication.
Macaulay says: “This sort of verse has been called [Namby Pamby] after the name of its author.”