φίλτρον properly φίλητρον, from φιλέω
1.a love-charm, (cf. Shakspeare's "medicines to make me love him"), ἐστὶν φίλτρα μοι θελκτήρια ἔρωτος Eur.; of the robe of Nessus by which Deianira hoped to win back the love of Hercules, Soph.
2.generally, a charm, spell, as a means of winning or influencing others, hence the bit is called φ. ἵππειον, Pind.; Apollo's oracles are φίλτρα τόλμης spells to produce boldness, Aesch.; children are a φίλτρον of love to their parents, Eur., etc.
3.in pl. love, affection, id=Eur.