philtrum : the vertical groove on the median line of the upper lip
They said although it looks like a nose bleed, it appears to be the shadow of Will's philtrum, or the vertical groove on the median line of the upper lip.
— Katie Palmer, Express (London, Eng.), 14 Jul. 2022
In Greek, the primary meaning of philtrum is "love potion" - which suggests that seductive powers were attributed to this facial feature.