TgJ Jer34:14 :וְיִפלְחִינָך שֵית שְנִין וְתִפטְרִנֵיה בַר חוֹרִין מֵעִמָך‏ : he should serve you for six years and then you should release him from you as a free person
See the entire entry for pṭr vb. to separate