One of the tasks facing Christian Hebraists was the difficulty of penetrating rabbinic literature. While lesser lights often mastered Biblical Hebrew, and even the ability to independently read Targums, the real heavy hitters also mastered the various styles of rabbinic Hebrew, how to read Hebrew without nekkudos, and the so-called Rashi script, to say nothing of the drastically foreign teachings and mentality contained in rabbinic literature.
Nothing illustrates this problem better than a quote like the following, from Andrew Reid's review of a work called Catalecta Rabbinica by David Mill, a work intended to facilitate the study of rabbinic literature. in the 1729 volume of The Present state of the republick of letters.
To remedy this the few who were able to read rabbinic texts in the original produced Latin translations of works ranging from certain tractates of the Talmud and Mishnah, commentaries on the Mishnah, parts of Maimonides' code, etc. Especially careful attention was paid to the subgenre within rabbinic literature about rabbinic literature.
It is with this in mind that the 17th century Dutch Hebraist Constantin L'Empereur (1591-1458) produced a translation of a 15th century guide to the Talmud called Halichos Olam, alongside the Mevo Ha-Talmud of R. Shmuel Ha-naggid (called Mevo Ha-Gemara here possibly because it was so titled in the text L'Empereur used; in the 16th and 17th century the use of the word "Talmud" in a book title was basically not allowed in Italy and other Catholic areas. "Gemara" was an acceptable substitution. Allegedly the common usage among Jews of the term "Gemara" to refer to the Talmud as a whole dates to this period). The Latin title he gave to his work was Clavis Talmudica, "Key to the Talmud."
Parranthetically, the competent Hebraists delighted in mastering the arcanae of rabbinic literature and using its forms correctly, which I would assume is why זצ"ל is appended to the names of the rabbis on the title page, and not merely because he had copied the names from his text. See here.
In 1714 this work was reissued in Hanau under the title Clavis Talmudica Maxima with the fore-title מפתח התלמוד הגדול, for now it included, a 16th century Talmud guide called Mafteach Ha-gemara, as well as the סוגיות התלמוד.
In 18th century England there was a Hebraist movement led and inspired by John Hutchinson that was what might be called anti-scientific. The Hutchinsonians (as they were called) eschewed the nekkudos as an untrustworthy accretion to the Hebrew language. Consequently they groped in the dark to understand Hebrew grammar, and constructed strange theories about the nature and meaning of Hebrew words. See, for example, the following page from David Levi's fascinating Lingua Sacra for a Hutchinsonian interpretation of the Hebrew word for God:
Several of John Hutchinson's works are online. In his The Hebrew Writings perfect - Alterations by Rabbies forged we find the following quote from the מפתח הגמרא, evidently taken from a work by the Hebraist Wagenseil responding to R. Yom Tov Lipmann Millhausen's Nizachon. The following list of rules of procedure are taken as evidence of the silliness of rabbinic literature (tt hardly goes without saying that rules for pesak such as these were meant to be descriptive):
It goes on to mention (of course) the tanur shel akhnai (continue reading here, pg. 179 in the digital copy).
Here's a sample of the 5th Gate of the Mafteach Ha-gemara where this is taken from:
It is interesting that John "I don't need no stinkin' vowel-points" Hutchinson writes רבי as Ribbi. See Shabbos 31a.
(Interestingly, according to R. Ya'akov Emden although "Ribbi" ("Rivi," really) is the correct Hebrew, davka the kinnui for Rabbenu ha-kadosh is pronounced "Rabbi," but that's all academic.)
And yes, D. stands for Doctor, as in "Doctor Yishmael," "Doctor Eliezer," etc.