Parashas Bo · Shemos 12:4 · TT note 13
Torah Temimah on Shemos 12:4, note 13 (on תָּכֹסּוּ) points to Pesachim 61a (R’ reading of the word as Aramaic for slaughter).
Sefaria — Exodus 12:4
Sefaria — Torah Temimah on Exodus 12:4
Sefaria — Pesachim 61a
E-Daf — Pesachim 61a
English: Rabbi says: It is Aramaic usage, as when a person says to his fellow, “Slaughter (kos li) this lamb for me.”
Lexical derash: תָּכֹסּוּ is read as a verb of slaughtering, locking the enrollment requirement to the act of shechitah.
The word תָּכֹסּוּ itself denotes the slaughter performed for those enrolled on the Pesach.