escape character (\)
Definition - One of the many names for the \ symbol.

Etymology -
The term escape character arose from the field of computing science in the latter half of the 20th century. In that field, it denotes a code used to indicate that subsequence characters should be interpreted differently.

Oxford English Dictionary -
The phrase's first citation is from 1962:
"*Escape character, a character used to indicate that the digit which follows is to be interpreted as belonging to a different alphabet."
(Gloss. Terms Automatic Data Processing (B.S.I.) 15)

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