unfertileness

“Un is prefixed to all words originally English, and to all participles made privitive adjectives, as, unfeeling; and to most substantives having an English termination, as, unfertileness; which, if they have a borrowed termination, take in, as, infertility.”

The Scholar's Spelling Assistant; Wherein the Words Are Arranged on an Improved Plan, According to Their Respective Principles of Accentuation. In a Manner Calculated to Familiarize the Art of Spelling and Pronunciation, to Remove Difficulties, and to Facilitate General Improvement Intended for the Use of Schools and Private Tuition

“Un is prefixed to most substantives which have an English termination, as unfertileness, unperfectness, which, if they have borrowed terminations, take in or im, as infertility, imperfection; uncivil, incivility; unactive, inactivity.”

A Grammar of the English Tongue