A bigram is any sequence of two consecutive letters found in a word, such as OG in dOG. A double bigram is a bigram that occurs twice in succession, such as OGOG in mOGOGraphia. Bigrams can be extended to triple, such as OGOGOG in lOGOGOGue, and quaduple, such as KUKUKUKU, which is itself a word.
"Double, Triple, and Quadruple Bigrams,"
Word Ways: Vol. 22
, Article 8.
Available at: http://digitalcommons.butler.edu/wordways/vol22/iss3/8