Why is it called an ark?

“Ark” is not a normal English word. We don’t use it for anything other than one big boat and one box in the Jewish temple. So where does it come from and why is it there in our English bibles?

The Hebrew word for the boat built by Noah is תֵּבָה (tebah). This word appears in the Bible in only two books: in Genesis in the story of Noah, and in Exodus where it's the word for the basket in which Moses floats on the Nile. This is not, contrary to our translations, the same word used for the chest containing the tablets of the 10 Commandments. That word is אֲרוֹן (aron), and it's used almost exclusively for the ark of the covenant (exceptions: Gn 50:26, 2 K 12:9-10, 2 Chr 24:10-11).

So, if it's not the same word in Hebrew, why do we use the same word in English? And why ark? The answer to the first question can be found in the Septuagint, the Greek translation of the Old Testament made by the Jews in the 3rd and 2nd centuries BC. There we find the same Greek word, κιβωτος (kibotos), which translates the tebah of Noah and the aron of the covenant. Kibotos has the meaning of “chest” or “box”. This then is translated in Latin in the Vulgate Bible as arca, and it's this word that became ark in English.