An isogram (also known as a "nonpattern word") is a logological term for a word or phrase without a repeating letter. It is also used by some to mean a word or phrase in which each letter appears the same number of times, not necessarily just once. Conveniently, the word itself is an isogram.
In the book Language on Vacation: An Olio of Orthographical Oddities, Dmitri Borgmann tries to find the longest isogrammic word. The longest one he found was "Dermatoglyphics"
at 15 letters. He coins several longer hypothetical words, such as
"thumbscrew-japingly" (18 letters, defined as "as if mocking a thumbscrew")
and, with the "uttermost limit in the way of verbal creativeness",
"pubvexingfjord-schmaltzy" (23 letters, defined as "as if in the manner
of the extreme sentimentalism generated in some individuals by the sight of a majestic fjord, which sentimentalism is annoying to the clientele of an English inn").
In the book Making the Alphabet Dance, Ross Eckler reports the word "subdermatoglyphic" (17 letters) can be found in Lowell Goldmith's article Chaos: To See a World in a Grain of Sand and a Heaven in a Wild Flower. He also found the name "Melvin Schwarzkopf" (17 letters), a man living in Alton, Illinois,
and proposed the name "Emily Jung Schwartzkopf" (21 letters). In an
elaborate story, Eckler talked about a group of scientists who name the
unavoidable urge to speak in pangrams the "Hjelmqvist-Gryb-Zock-Pfund-Wax syndrome".
The longest German isogram is "Heizölrückstoßabdämpfung" (heating oil
recoil dampening) with 24 letters, closely followed by
"Boxkampfjuryschützlinge" (box fight jury fosterlings) and
"Zwölftonmusikbücherjagd" (twelve-tone music book chase) with 23