A pair isogram is a word in which each different letter occurs exactly twice. As a genre, pair isograms can be divided into two types. We can call these split pair isograms (SPIs for short) in which the letters in the first half of the word are repeated, in a different order, in the second half (HORSESHOER); and non-split pair isograms (NSPIs) in which this is not the case (APPEASES).
"On Location With Pair Isograms,"
Word Ways: Vol. 37
, Article 6.
Available at: http://digitalcommons.butler.edu/wordways/vol37/iss1/6