From The Art and Popular Culture Encyclopedia
The term gratuitous means given freely; unearned. It also signifies not called for by the circumstances; uncalled-for; without reason, cause, or proof; adopted or asserted without any good ground; unjustified.
In narratology the term denotes seeking sensationalism or without having reasons, rationales or pretexts to do so. The term is usually encountered in contexts of sex (see the pornography/erotica debate) or violence. The word stems from the Latin gratuitus, which means free.
From Latin gratuitus (“free”), from Latin gratia (“favor”), gratus (“showing favor”).