AutoItalicWords is an option for Cell which gives a list of words which should automatically be put in italics when they are entered.
Typical settings for AutoItalicWords include "Mathematica" and "MathLink".
AutoItalicWords affects only ordinary text strings, not elements of more general expressions.
See The Mathematica Book: Section 2.10.11.
See also: FontSlant, SingleLetterItalics.