EAST’S FIRST DISCARD IS A JOKER (Article 35) 

Commentary: East always discards to start the game. Although it is rare, they may discard a joker and when they do, it should be named, “joker.” This is an indicator that they could be playing a pure hand, or a singles and pair hand.

Question from a player:  When East is playing a pair hand and has a joker for their first discard, what would it be called? 
 
Answer from the NMJL:  “She may only name it “joker”.” 

Source: National Mah Jongg League Bulletin Q&A (2003)

Other answers from the league: 
 
“The one exception to the rule back of scorecard.  If at the end of the Charleston East wishes to discard a joker in order to be set for a jokerless hand, she may discard the joker and call it joker as she cannot call it the name of the previous tile.” 
 
“There is one exception to discarding a joker and calling it the same name of the previous discard.  If East wishes to discard a joker for the first discard, she may call it joker as there is no previous name to call it.” 
 
“If East has two odd jokers at the end of the Charleston and wishes to play a jokerless hand, the procedure is the first joker discard (East only) must be called “joker” and remains on the table as a “dead” tile and the next joker discard must then be called the name of the previous discard, as usual, and remains on the table as a “dead” tile.” 
 
If East has a joker at the end of the Charleston and wishes to play a jokerless hand, the joker may be discarded and it must be called “joker” and remain on the table as a dead tile.  At all other times, a discarded joker may be called the  name of the previous discard, as usual and remain on the table as a dead tile.”  
 
Source:  National Mah Jongg League Bulletin Q&A (1972 page 4, 1973 page 4, 1974 page 3, 1975 page 4, 1977 page 3, 1977 page 4, 1978 page 3, 1979 page 3, 1981 page 4, 1983 page 3, 1995 page 4, 2003)  https://www.nationalmahjonggleague.org