A computer search for seven-letter word squares that can be made from words in Webster's Collegiate Dictionary, 7th edition, turned up only 52 examples. Specifically, these were constructed from a corpus of 9663 seven-letter words: single words listed in boldface type in the main body of the dictionary (including proper names), and names from the appendices of boys' and girls' first names. had this corpus been expanded to include inferred words not given in boldface, such as plurals of nouns, -ING and -ED forms of verbs, and -ER and -EST forms of adjectives, many more squares would have been found, including at least four of the eight 7x7 word squares presented by Dmitri Borgmann at the start of Chapter 7 in Language on Vacation (Scribner's, 1965).
McIlroy, M. D.
"7x7 Computer-Generated Word Squares,"
Word Ways: Vol. 8
, Article 2.
Available at: http://digitalcommons.butler.edu/wordways/vol8/iss4/2