The name 'Codex Sinaiticus' literally means 'the Sinai Book'. It reflects two important aspects of the manuscript: its form and a very special place in its history.
'Codex' means 'book'. By the time Codex Sinaiticus was written, works of literature were increasingly written on sheets that were folded and bound together in a format that we still use to this day. This book format was steadily replacing the roll format which was more widespread just a century before when texts were written on one side of a series of sheets glued together to make a roll. These rolls were made of animal skin (like most of the Dead Sea Scrolls) or the papyrus plant (commonly used for Greek and Latin literature).
Using the papyrus codex was a distinctive feature of early Christian culture. The pages of Codex Sinaiticus however are of prepared animal skin called parchment. This marks it out as standing at an important transition in book history. Before it we see many examples of Greek and Latin texts on papyrus roll or papyrus codex, but almost no traces of parchment codices. After it, the parchment codex becomes normative.
During its history – particularly its modern history – parts of Codex Sinaiticus were also known by other names. The 43 leaves which are now at Leipzig University Library were published in 1846 as 'Codex Frederico-Augustanus' in honour of Frederick Augustus II, King of Saxony, who was the patron of the German Biblical scholar and editor of Codex Sinaiticus, Constantine Tischendorf. The 347 leaves now in The British Library were previously known as 'Codex Sinaiticus Petropolitanus', as they were kept in St Petersburg between 1863 and 1933.