Transaddition
This flat type is normally done as a transdeletion. But see also group flats, Charade, and the following two exceptions.
In a Rochester transaddition, each letter in a word is added back to the word, in order, and the result transposed. Examples: nacre; canner, arcane, cancer, craner, careen; and scare; caress, scarce, Caesar, racers, crease; and heart; hearth, heater, Aretha, rather, threat.
The Rochester transaddition was invented by Hap.
A Bridgewater transaddition is a generalization of the Rochester transaddition. You begin with an n-letter BASE word and an m-letter BANK word (note: n and m do not need to be equal). The other solution words are formed by transposing all the letters in BASE plus each of the m letters from BANK in turn. (A Rochester transaddition is a Bridgewater transaddition where BASE and BANK are the same word.) Example: BASE = cast iron, BANK = atone, ONE = raincoats, TWO = tractions, THREE = consortia, FOUR = transonic, FIVE = creations. Another example: BASE = east, BANK = Xemu, ONE = Texas, TWO = tease, THREE = teams, FOUR = saute.
The Bridgewater transaddition was invented by Xemu, named by Meki, and introduced in January 1996.