Chazal's source of knowledge

  Megila (18a) Rosh HaShanna (26b) In a certain place which Levi happened to visit, a man came before him and said , So-and-so has kaba'ed me. He did not know what he meant, so he went and enquired in the Beth Hamidrash. They said to him: He wanted to say to you, has robbed me, as it is written, Will man rob God? Raba from Barnish said to R. Ashi: Had I been there, I should have said to him, How did he kaba you, in what did he kaba you, why did he kaba you, and so I should have found out from his answers. Levi, however, thought that he meant some kind of offence. The Rabbis did not know what was meant by serugin till one day they heard the maidservant of Rabbi's household, on seeing the Rabbis enter at intervals, say to them, How long are you going to come in by serugin?The Rabbis did not know what was meant by haluglugoth till one day they heard the handmaid of the household of Rabbi, on seeing a man peeling portulaks, say to him, How long will you be peeling your haluglugoth? The Rabbis did not know what was meant by salselehah and it shall exalt thee. One day they heard the handmaid of the household of Rabbi say to a man who was curling his hair, How long will you be mesalselwith your hair?The Rabbis did not know what was meant by we-tetethia bematate of destruction, till one day they heard the handmaid of the household of Rabbi say to her companion, Take the tatitha [broom] and tati [sweep] the house. The Rabbis did not know what was meant by Cast upon the Lord thy yehab and he shall sustain thee. Said Rabbah b. Bar Hanah: One day I was travelling with an Arab and was carrying a load, and he said to me, Lift up your yehab and put it on one of the camels.