Quoting Commentary for Exodus 6:1

A calling, an expression of love. [All the “speakings,” etc.] in the Tent of Meeting were preceded by a calling. That is to say, from here we learn through a בנין אב (by comparison) that whenever it says, וידבר, ויאמר, or צו, it was preceded by calling. This is so in the case of דיבור as explained here. אמירה: as it is written in Parshas Shemos (3:4): “Elohim called to him from the midst of the thorn-bush, and said (ויאמר).” ציווי: as it is written in Parshas Yisro (19:20): “And Adonoy called to Moshe to come up to the top of the mountain ... [Adonoy] said ... ‘Go down and warn the people...’ This is an expression of ציווי: Lest they break through toward Hashem to see. However, there remains a difficulty: Why did Rashi not give this explanation above in Parshas Shemos or Yisro; why did he leave it until now? (Minchas Yaakov and Nachalas Yaakov).

A Midrashic approach based on Tosafot Gittin 2, (dibur hamatchil “המביא”). The word ספר כריתות includes that there must be (at least) twelve lines; just as in the Torah scroll (known as the Book of the Torah) one needs to leave 4 lines empty at the end of the Book of Genesis before commencing to write the Book of Exodus, and the same at the end of the “book” of Exodus, and again at the end of the “book” of Leviticus,” (making a total of twelve lines), so the Get, i.e. bill of divorce, has to correspond in appearance to such a “book” of the Torah. [At the end of the Book of Numbers there are no mandatory empty four lines as this “book” is considered the last “book” of the Torah, Deuteronomy being known as Mishneh Torah, a review of the Torah].
Onkelos translates the words ספר כריתות as גט פטורין, “a document of release.” Seeing that this document is called ספר by the Torah, it requires that it be written in a similar manner to the Torah. The word גט has a numerical value of 12, i.e. alludes to the requirement to have 12 lines.

A letter was added to his name. Re”m asks: If so, there are only six names! Before he converted he was called Yeser and not Yisro. After he converted he was called Yisro and not Yeser. They should not be considered as two names, just as Avram and Avraham should not be considered as two names. Re”m leaves this question unanswered. But it seems to me not to be a question, for Rashi does not say, “He has seven names.” He rather says, “He was called by seven names.” I.e., some names he was called before he converted, and some, afterward. (Maharshal) Yet, it seems to me there is no proof that his name was [always] Yeser until he converted. Perhaps he [originally] had a different name. For Rashi also explained the verse, “Moshe went and returned to Yeser his father-in-law” (4:18), that Yisro was called seven names, just like Rashi explains here — but that was before Yisro converted and before he caused an additional parsha in the Torah. Perforce, he had a different name before he converted, and there the Torah called him “Yeser” based on a future event. In truth, when he came and advised Moshe how to judge the people, he was immediately called [the new name of] Yeser, because he caused this additional parsha in the Torah. And this occurred before he converted. After he converted, the letter ו was then added [to his name]. Thus, he was called seven names in addition to his original, nonJewish name. We need not object: In Parshas Shemos it said, “Moshe went and returned to Yeser, his father-in-law,” implying that his nonJewish name was Yeser. For this is no proof, as it is also written there, “Moshe tended the sheep of his father-in-law Yisro” (3:1),” [though Yisro had not yet converted]. Perforce, [he was called Yeser and Yisro] based on a future event, as I explained. (Author’s commentary)