Biographical details for William Diaper are sparse. He was born in Bridgwater, the son of Joseph Diaper, and attended Balliol College, Oxford in 1699 as a poor scholar (pauper puer), and took his BA degree in 1705.
In 1709 he was ordained as a deacon and became a curate in the parish of Brent Knoll, overlooking the Somerset Levels, which he made the subject of his humorous first poem. His next set of poems, the innovative Nereides, or Sea-Eclogues, was published in 1712 and earned him entry into the London literary world.