diarrh... тьфу, diaere... тьфу, блин. поносоник.
Новости о запретной букве:

A dieresis (also diæresis or diaeresis) is a mark in the form of a pair of dots (¨) over the second of two adjacent vowels to indicate that it is to be pronounced in a separate syllable from the first.

Some words in English that have come from foreign languages that use diereses have retained them over the years. It is usually optional to include them, but two such words that are frequently spelled with dieresis intact are naïve and noël. Additionally, there are a few names that are commonly spelled with a diaresis, such as Zoë, Noë, Chloë, Noël, and Noëlle.

Some people prefer to use a diaresis over the second of a pair of identical vowels, when they are pronounced separately, and not as a single vowel. Compare coop (as in "a chicken coop") to coöp (as in "a health-food coöp"). Though there have been times when this style was popular, it has has become fairly uncommon—so much so that The New Yorker is famous amongst stylists and editors as the only well-known publisher that still insists upon it. Some common words that are affected by this style are coöperate, reënact, reëlect, and noöne.