The King James Version translates the Jews' reaction to seeing manna as follows (Exodus 16:15):
And when the children of Israel saw it, they said one to another, It is manna: for they wist not what it was.This is probably the worst possible translation of "ויראו בני-ישראל, ויאמרו איש אל-אחיו מן הוא--כי לא ידעו, מה-הוא"
The 1917 JPS translation has it as:
And when the children of Israel saw it, they said one to another: 'What is it?'--for they knew not what it was.The interpretorial question is what "מן" means in the phrase "מן הוא".
Rashi says that "מן" means food, and so the Artscroll Stone Tanach translates it as "It is food". The Bekhor Shor suggests that the word derives from ancient Egyptian and means "what", in the sense of "What is it?", as the JPS translation renders it. The Rashbam and Chizkuni interpret similarly.
Interestingly, Ibn Ezra quotes that interpretation in the name of a R. Shlomo but that it comes from Arabic rather than Egyptian. The Ibn Ezra then disputes this interpretation based on his knowledge of Arabic.
The Bekhor Shor's interpretation received support, to a degree, from archaeological finds. Cassuto points out that ancient Canaanite language uses "מן" to mean "what", as evidenced in Ugaritic poetry and the El Amarna Letters. While Bekhor Shor claims that the word comes from Egyptian, the archaeological evidence suggests that it comes from ancient semitic languages. Either way, the meaning is the same and indicates that the JPS translation has a very solid basis.