Semordnilap (palindromes spelled backward) is a name coined for words that spell a different word in reverse. The word was coined by Martin Gardner in his notes to C.C. Bombaugh's book Oddities and Curiosities of Words and Literature in 1961.
An example of this is the word stressed, which is desserts spelled backward.
Some semordnilaps are deliberate creations. An example in electronics (although rarely used now) is the mho, a unit of electrical conductance, which is ohm spelled backwards, the unit of electrical resistance and the reciprocal of conductance. Similarly, the daraf, a unit of elastance, is farad spelled backwards, the unit of capacitance and the reciprocal of elastance. In fiction, many characters have names deliberately made to be semordnilaps of other names or words, such as Alucard (a semordnilap of "Dracula").
Semordnilaps are also known as emordnilaps, word reversals, reversible anagrams, heteropalindromes, semi-palindromes, half-palindromes, reversgrams, mynoretehs, volvograms, or anadromes. They have also sometimes been called antigrams, though this term usually refers to anagrams which have opposite meanings. As of October 2018, none of these terms have been accepted as official entries in the Oxford English Dictionary.
