EXTRA · Parashas Vayeishev · Passuk 38:3 · not a Torah Temimah citation on this passuk
She conceived and bore a son, and he named him Er.
Classical source (EXTRA side-ring): Yalkut Shimoni 145.
English: “And he called his name Er” — a son who was emptied (hu’ar) from the world.
Derash on the verse (Yalkut) — not a formal named middah of the 13. The name is read as a hint to his fate.
Er’s name already signals that he would be removed from the world before his time.