While the concept may have existed far prior, a recent discussion has left me wondering - What is the earliest documented usage of the term "Sola Scriptura" in Christian writings. I am not interested in articulation of the concept, but instead of the first documented usage of this specific and actual phrase in reference to the doctrine (not just coincidental usage) - so please be sure to include a quote in your answer.
In 1520 Luther wrote the following in his defense against the bull of Pope Leo X:
Nolo omnium doctior iactari, sed solam scripturam regnare, nec eam meo spiritu aut ullorum hominum interpretari, sed per seipsam et suo spiritu intelligi volo. (WA 7:98.40–99.2)
Mark D. Thompson gives this translation:
I do not want to throw out all those more learned [than I], but Scripture alone to reign, and not to interpret it by my own spirit or the spirit of any man, but I want to understand it by itself and its spirit.
The first documented usage of the specific and actual phrase ''Sola Scriptura'' in reference to the doctrine was as late as the 20th century.
The solas were not systematically articulated together until the 20th century. But sola gratia and sola fide were used in conjunction by the Reformers themselves. For example, in 1554 Melanchthon wrote, "sola gratia justificamus et sola fide justificamur" ("only by grace do you justify and only by faith are we justified"). All of the solas show up in various writings by the Protestant Reformers, but they are not catalogued together by any.
In 1916, Lutheran scholar Theodore Engelder published an article titled "The Three Principles of the Reformation: Sola Scriptura, Sola Gratia, Sola Fides", ("only scripture, only grace, only faith"). In 1934, theologian Emil Brunner substituted Soli Deo gloriam for Sola Scriptura.In 1958, historian Geoffrey Elton, summarizing the work of John Calvin, wrote that Calvin had "joined together" the "great watchwords." Elton listed sola fide with sola gratia as one term, followed by sola scriptura and soli Deo gloria. (source).
According to Protestants,
These “five solas” were developed in response to specific perversions of the truth that were taught by the corrupt Roman Catholic Church. (source).