Today’s word comes with little to no explanation: philtrum. Philtrum arrived in English at the height of the English literary renaissance around 1600-1610 as an anatomical term to describe the small indentation below the nose and above the mouth. The word itself comes from a Late Latinization of the Ancient Greek word philtron (φίλτρον) meaning a love potion from the Ancient Greek verb philein (φιλεῖν) meaning to love. Liddel and Scott’s Ancient Greek Lexicon offers this definition of philtron: a love charm, a spell to produce love, Shakespeare’s ‘medicine to make me love him’, generally a charm, spell. It isn’t everyday that word research has an Ancient Greek Lexicon refer forward 1800 years or so to Shakespeare, but perhaps there is an Elizabethan connection between the word that is now lost. Most mammals also have philtra (see the canine philtrum above, and thanks, Stella!).
Images of famous philtra (despite the mixed etymological heritage of the word, the plural is given from the Latin neuter).