Many Word Ways articles have dealt with words differing from each other in only a single letter (such as SHARE and SHORE, in which A is replaced by O and the other letters are left untouched). Word ladders form HEAD HEAL TEAL TELL ... have been constructed for nearly a century (does any reader know of a reference prior to Lewis Carroll's Doublets which was published in 1879?). More recently, Ross Eckler (February, 1969) demonstrated that replacements can be found not only for the A-O pair but also for the other 324 possibilities. Dave Silverman (May 1970, February 1972) has been interested in both isolanos (words in which no letter can be replaced to form another word) and onalosis (words in which any letter can be replaced to form another word). Rudolph Castown (August 1968) and Leslie Card (November 1970, February 1971) have developed the concept of a garble group -- a completely interlocked word set such as BIG BAG BUG BIT BAT BUT BID BAD BUD BIN BAN BUN.
Peterson, Palmer C.
Word Ways: Vol. 5
, Article 18.
Available at: https://digitalcommons.butler.edu/wordways/vol5/iss2/18