An alphabetic insertion occurs when each letter of the alphabet is inserted in turn in the same position within an n-letter word, forming 26 new words of length n+1. Alphabetic insertions are extremely difficult to find, even for the simplest case in which letters are in tern inserted in the center of a two-letter word. As a practical matter, the only alphabetic insertions with any hope of success are those in which the original word consists of two vowels; letting x and y stand for vowels, the 26 words sought are of the form xay, xby, xcy, ... , xzy.
"A Palindromic Alphabetic Insertion,"
Word Ways: Vol. 15
, Article 5.
Available at: https://digitalcommons.butler.edu/wordways/vol15/iss4/5