In the 1982 film Blade Runner, a group of six humanoid androids (referred to as "replicants") have violently rebelled against their masters and escaped to Earth in search of a means of prolonging their artificially-short lifespans. The leader of this group of fugitives is a replicant named Roy Batty, and they are being tracked down by retired bounty hunter (referred to as a "blade runner") named Rick Deckard.
Two of the replicants are killed offscreen by blade runner Dave Holden, who is then shot by the replicant Leon while administering a Voight-Kampff test in an attempt to determine Leon's identity. Deckard proceeds to "retire" (in other words, kill) the remaining fugitive replicants one by one, starting with Zohra, then Leon, and then finally Pris shortly before being confronted by Batty.
During their encounter, Batty addresses Deckard by name, and speaks as if he is familiar with him (starting at 1:13 in the following video):
Batty: Not very sporty to fire on an unarmed opponent. I thought you were supposed to be good. Aren't you the "good man"? Come on, Deckard. Show me what you're made of.
However, Batty didn't meet Deckard prior to this. And the only other replicants in his group who did were all retired shortly after meeting him, so none of them had the chance to tell him, even if they had learned his name. And I don't recall any scene where Batty looks him up or learns anything about him.
So, how did Batty know Deckard's name?