The Gemara tells of someone who approached Reish Lakish, telling him that he was certain that a specific person was a kohen. He knew this because he saw that he had been called up first to the Torah reading. Resh Lakish responded by asking him whether he had also seen this man receiving teruma when it was being divided up at the granary. Rabbi Elazar overheard this and responded, “and if there is no granary in the town, can we not establish who is a kohen?” That is to say, the testimony based on the Torah reading should be sufficient. On another occasion, Reish Lakish was sitting with Rabbi Yohanan and a similar conversation ensued. When Rabbi Yohanan said “and if there is no granary in the town, can we not establish who is a kohen?” it became clear to Reish Lakish that Rabbi Elazar had learned this from Rabbi Yohanan. The next time he saw Rabbi Elazar he said to him “you learned that from bar Nappaha (Rabbi Yohanan)! Why didn’t you quote it is his name!?”
Most of the commentaries accept Rashi’s approach to Reish Lakish’s complaint – had he known that the argument Rabbi Elazar had raised was the opinion of Rabbi Yohanan, he would have accepted it the first time he heard it. Rabbeinu Hananel suggests that even if he would not have accepted it, in Rabbi Yohanan’s presence he would not have stated a position to which he knew Rabbi Yohanan objected. The Ritva explains that the reason Rabbi Elazar did not quote Rabbi Yonanan is because the relationship between the two was so close that he believed that it should have been clear to everyone that the statements he made were those he learned from his teacher, Rabbi Yohanan.
On several occasions in the Talmud – most often in the Talmud Yerushalmi – Rabbi Yohanan is referred to as bar Nappaha – “son of a blacksmith.” Some suggest that this is simply because that was his father’s occupation. Others suggest that it was an ironic nickname given to Rabbi Yohanan specifically because of his good looks, while another approach suggests that it refers to his strength and proficiency in Torah.