Back when people spoke more than one language:
Chaucer’s Treatise on the Astrolabe, written in the 1390s for his ten-year-old son, Lewis, is an English translation of a Latin version of an Arabic text written by Mashallah ibn Athari, an eighth-century Persian Jew. In the prologue, Chaucer says that Lewis only knows a little Latin, but is good with numbers, and so the treatise will teach him how to use the astrolabe he has just been given as a present. After all, Chaucer says, the facts remain the same whether Hebrew, Arabic, Latin, Greek or English is used; he himself is a compiler, bringing together the work of old astrologers into ‘naked words in englissh’. (Stop talking englissh: Medieval Polyglots)
However: I guess we should also consider that not everybody back then spoke multiple languages? Maybe yes, maybe no. Empires of the Word — another wonderful book about language(s) — does say something about this.