Definition - The incorrect repetition of letters or words when making a written copy of a text.
Note: A repeated letter of this type is called a dittograph.

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

Etymology -
The term derives from a Greek word meaning "double writing."

Oxford English Dictionary -
Its first citation is from 1876:
"The ge may be merely a scribal error—a repetition (dittography) of the preceding ge."
(H. Sweet A.S. Rdr. Notes (1879) 202)

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