The phrase by the skin of one’s teeth means by a very narrow margin; only just.
This is a reference to the Book of Job*, 19:20, which is, in the New International Version (2011):
I am nothing but skin and bones;
I have escaped only by the skin of my teethᵃ.
ᵃ or only by my gums
(* Job was a prosperous man whose patience and piety were tried by undeserved misfortunes, and who, in spite of his bitter lamentations, remained confident in the goodness and justice of God.)
In the King James Version (1611), which helped to make the phrase proverbial in English, the verse is:
My bone cleaueth to my skinne, and to my flesh, and I am escaped with the skinne of my teeth.
The King James Version followed the text of the 1560 Geneva Bible (the primary Bible of 16th-century Protestantism), which itself translated literally the biblical Hebrew bĕʿōr šinnāi, with the skin of my teeth.
The sense of the passage in Job is uncertain and disputed (one explanation is that skin refers to the gums, another is that it refers to the enamel coating of the teeth), as are the grammatical analysis and meaning of the Hebrew verb form immediately preceding the noun phrase. Many recent commentators doubt that the Hebrew text offers any support for the notion of a narrow escape. It is possible—and that would fit its context—that the second half of the verse means I have lost everything.
In fact, there is so much confusion and uncertainty that the Greek Septuagint and the Latin Vulgate each render the passage differently from the above-mentioned versions.
The Septuagint is a Greek version of the Old Testament, made for Greek-speaking Jews in Egypt in the 3rd and 2nd centuries BC and adopted by the early Christian Churches. (The word Septuagint is from Latin septuaginta, seventy, because of the tradition that it was produced, under divine inspiration, by seventy-two translators working independently.)
The Vulgate is the principal Latin version of the Bible, prepared mainly by St Jerome in the late 4th century, and (as revised in 1592) adopted as the official text for the Roman Catholic Church.
In the Septuagint (which apparently followed an emendation of the Hebrew text), the passage is:
τὰ δὲ ὁστᾶ μου ἑν ὁδοῦσιν ἔχεται (my bones are held in my teeth)
In the Vulgate, it is:
derelicta sunt tantummodo labia circa dentes meos (only my lips are left around my teeth)
The Early Version (around 1382) of the Wycliffe Bible followed the text of the Vulgate:
onli the lippis ben lafte aboute my teth
John Wycliffe (circa 1330-1384), an English religious reformer, instituted the first English translation of the complete Bible. He criticised the wealth and power of the Church and upheld the Bible as the sole guide for doctrine. His teachings were disseminated by itinerant preachers and are regarded as precursors of the Reformation. His followers were known as Lollards.
In the Coverdale Bible (1535), the passage is:
only there is left me the skynne aboute my teth
Miles Coverdale (1488-1568), an English biblical scholar, translated the first complete printed English Bible (1535), published in Zurich while he was in exile for preaching against confession and images. He also edited the Great Bible of 1539.