Definition of "fellatio"

In 7 oder 8 anderen Fällen ging die geschlechtliche Beziehung selten über enge Berührung oder gegenseitige Masturbation hinaus. In 2 oder 3 anderen Fällen ist fellatio die bevorzugte Methode.In eight or nine [sic] cases the sexual relationship rarely goes beyond close physical contact, or at most mutual masturbation. In two or three cases fellatio is the form preferred.

1897, Havelock Ellis, Das Konträre Geschlechtsgefühl [Sexual Inversion] (in German)

That the word "fellatio" has not become Anglicized is so clearly apparent that further comment seems unnecessary. […] Section 288a of the Penal Code is void for uncertainty as well as for the reason that it is not expressed in the English language.]

[1919 January 9, Supreme Court of California, In re Lockett, 57 Cal. Dec. 96