For the cover of a book about the English language, David Pearson chose a typeface with English roots. Caslon Rounded dates back to 1836. Specimens from 1842 and 1861 in the collection of St Bride Printing Library show solid, open, and decorated variations.
The first rounded typefaces appeared almost simultaneously on both sides of the Atlantic during the 1830s, in wood in the USA and in metal from the Caslon foundry. — Commercial Type
A digital interpretation was designed by Paul Barnes and Christian Schwartz in 2015. Their Caslon Rounded has one filled weight with italics and one shaded weight with layers. As of 2018, it’s unreleased.