Parashas Chayei Sarah · Passuk 25:6
but to Avraham’s sons by concubines Avraham gave gifts while he was still living, and he sent them away from his son Yitzchak eastward, to the land of the East.
Torah Temimah points to Sanhedrin 91a. E-Daf · Sefaria — Sanhedrin 91a
TT lemma: מתנות.
What are “gifts”? Rabbi Yirmiyah bar Abba said: This teaches that he transmitted to them a name of impurity.
Custom (Bavli — gifts of the names of impurity)
The “gifts” Avraham gave the sons of the concubines included the names of impurity, so that they would call their idols by those names and not misuse the Divine Name.