Florean Fortescue was the owner of an ice cream parlor in Diagon Alley. Florean knew quite a bit about history; When Harry was living at the Leaky Cauldron for a couple of weeks in August of 1993, he spent part of his days working on his homework at Florean’s shop. Florean gave him free sundaes every half hour and helped with his essay on medieval wizardry (PA4). Florean is a descendant of Dexter Fortescue, an ex-headmaster of Hogwarts (Pm, OP27, DH36).
Fortescue was one of the first victims of Death Eaters in the Second Wizarding War (late June or early July 1996). when he was dragged off from his shop and killed (HBP6).
According to behindthename.com, the name Florian (note that this is spelled with an "i" where Fortescue's first name is spelled with an "e") derives its meaning from the Latin word for flower. The name also sounds like the related word "florid" and could possibly have been chosen by Rowling to reflect his appearance. -BB
Rowling hinted in an interview that there was more to him than was revealed in the books (PC/JKR2). Later, on Pottermore, she described the ghost plot involving Fortescue. She intended him to be a sources of information for Harry about legendary items like the Elder Wand and the Diadem of Ravenclaw, and planned for Harry to rescue Florean in book seven. However, other characters took over the position of giving the information Harry needed, and poor Florean Fortescue was kidnapped and killed for nothing. Rowling said she feels a little guilty about the way he needlessly met his end (Pm).