Commentary for Genesis 37:36

הטבחים— means the slaughterers of the kings animals.

OFFICER OF ‘HATABACHIM.’ This means the slaughterers of the king’s animals. This is the language of Rashi. Similarly, it says, And the ‘tabach’ (cook) took up the thigh;¹⁰²I Samuel 9:24. For perfumers and for cooks ‘tabachoth’.¹⁰³Ibid., 8:13.
Closer to the meaning of the word hatabachim is the opinion of Onkelos who says that since the prison house was under his charge, [he was called the officer of the tabachim, since] we find the word t’vichah in connection with the killing of people. Prepare ye the slaughter (‘matbiach’) for his children;¹⁰⁴Isaiah 14:21. Thou hast slaughtered (‘tavachta’) unsparingly.¹⁰⁵Lamentations 2:21. The verse in the book of Daniel is proof of the validity of Onkelos’ interpretation: To Arioch the captain of ‘tabachaya’ of the king, who was gone forth to slay the wise men of Babylon.¹⁰⁶Daniel 2:14. The word tabachaya or tabachim is thus clearly associated with the slaying of people. See my Hebrew commentary, Note 77, pp. 211-212.

והמדנים מכרו אותו אל מצרים. The Midianites, Medanites, and the Ishmaelites are brotherly tribes. (compare 25,20) According to the plain meaning of the text, they are the same people, sometimes called by one name, other times by the other name. This is why the Torah wrote here that the Midianites had sold him, whereas the Ishmaelites had transported him there.