The barrow appears to have had the name since at least 1777, when it was marked on Taylor’s Map of Gloucester as “Paul Aposd”.
“It has been suggested that an epistle was read there at the beating of the parish bounds, which run close by. In the mid 19th century, however, the name ‘Paul and the Epistles’ was sometimes used and was said to refer to the number of trees.”
From: ‘Parishes: Dowdeswell’, A History of the County of Gloucester: volume 9: Bradley hundred. The Northleach area of the Cotswolds (2001), pp. 42-69. URL: british-history.ac.uk/report.aspx?compid=66462
Rather less religiously, it is also known locally as “Bull’s Pissel”!