Etymology Italian filtro (1598 as philtro in senses 1 and 2). With sense 2 compare slightly earlier philtrum Philtrum- Etymology: < classical Latin philtrum love-potion, in post-classical Latin also groove in the upper lip below the nostrils (1587 in a British source) < ancient Greek ϕίλτρον love-charm, love-potion, charm, spell, in Hellenistic Greek also dimple in the upper lip < ϕιλ- , stem of ϕιλεῖν to love

Definition of Philter

1. A potion, drug, or (occasionally) charm supposed to be capable of exciting sexual attraction or love, esp. towards a particular person; a love potion. Also, more generally: any potion or drug having supposedly magical properties. Also fig. (source Oxford English Dictionary)