TgO Ex40:15var. :וֻתהֵי לְמִהוֵי לְהוֹן רְבוּתְהוֹן לְכהוּנַת"לכהנות"לשמושת" עָלַם‏ : it should be for their anointment to the priesthood/ministry/ forever
See the entire entry for kāhnū, kāhnūṯā n.f. priesthood

TgO Ex40:15 var. :לְכהֻונַת"לשמושת" עָלַם‏ : for perpetual priestly service†
See the entire entry for šmwšh n.f. service