13.4: §90. Interesting Words
The -bilis and -ilis suffixes have given rise to many intriguing English words. Behind impeccable (L impeccabilis ) lies the verb peccare (“sin”); behind indefatigable , fatigare (“weary”). The base of inexorable (L inexorabilis ) is orare (“beg,” “pray”), so that the adjective means “unable to be prayed away.” The nouns terminus (“end”) and radix , radicis (“root”) underlie the denominatives interminable (L in-termin-abilis) and ineradicable (L in-e-radic-abilis ). In fate, fable, fame, and infant, we have met the Latin verb fari , fatus (“speak”); affable ( affabilis ), now “polite” or “courteous,” originally meant “able to be spoken to” ( ad- ); ineffab le still means “unable to be spoken out” ( ex- ). An appetite that is insatiable is “unable to get enough” ( satis ). A dirigible is an airship that can be directed or steered. What would you make of imperceptible and incorrigible?
Don’t confuse incredible and incredulous , which are both derived from credere , creditus (“believe,” “trust”). Whereas incredible (L incredibilis ) means “not able to be believed,” incredulous (L incredulus ) means “inclined to disbelieve.” If a department store bargain price is in credible , we should probably be incredulous .
Sometimes Latin verb stems could be modified by phonetic changes. Even in classical Latin, “able to move” ( movere , motus ) was mobilis , E mobile ; and “something easily poured” ( fundere , fusus ) was fut(t)ilis , E futile. By now, you have probably wondered about able itself. It evolved from L habilis ( habere ), just as ability derived from Latin habilitas . (At this point, would it be futile to offer a little re-hab-il-it-at-ion? )