Definition - A letter or word that is incorrectly repeated by a copyist who is making a written copy of a text.

Example -
When making the first written copy of the Ten Commandments, the scribe accidentally writes: Thou shalt not not kill.

Etymology -
The word derives from the Greek dittos, double + gramma, letter of the alphabet.

Oxford English Dictionary -
Its first citation is from 1881:
"The mora of ‘moram’ may be a dittogram from -m orationis."
(Athenæum 16 July 77/2)

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