fellatio

Etymology

Borrowed from Latin fellātio, from fellātus, perfect participle of fellō (“I suck, I fellate”). The word started to appear in medical literature in the 19th century but it was still treated as Latin. In 1919 the California Supreme Court struck down a law criminalizing "fellatio" because the state constitution required laws to be written in English. By the late 20th century fellatio was treated as an English word.

noun

1. The stimulation of the penis using the mouth.
   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 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