One of the many projects that has engaged the attention of serious-minded logologists has been the quest for words featuring one particular letter a substantial number of times. For instance, AMALGAMATED is a word with four A's; REFEREE uses for E's; and TUMULTUOUS includes four U's.
Borgmann, Dmitri A.
"The Multiple-Letter Word Hunt,"
Word Ways: Vol. 2
, Article 12.
Available at: https://digitalcommons.butler.edu/wordways/vol2/iss1/12