Do you suppose it's the umlauts?
"Fanny Herself" by Edna Ferber
UMLAUT, name given by Grimm to the modification of a vowel in a syllable through the influence of a vowel in the succeeding.
"The Nuttall Encyclopaedia" by Edited by Rev. James Wood
There is no trace of such vocalic mutation ("umlaut") in Gothic, our most archaic Germanic language.
"Language" by Edward Sapir
UNACCENTED VOWELS AND UMLAUT.
"A Middle High German Primer" by Joseph Wright
Beaufort is neither Bofort nor Boofort nor Biufort, but Bueft, the u pronounced like the umlauted u in German.
"Letters from Port Royal" by Various
Also, following a practical and common convention, I have replaced the umlaut with a following letter "e".
"Practical Taxidermy" by Montagu Browne
The presence of a Hunnish =umlaut= over the =u= adds insult to injury!
"Writings in the United Amateur, 1915-1922" by Howard Phillips Lovecraft