Hokey

Hokey was a house-elf that belonged to Hepzibah Smith.

Hokey was accused of poisoning her mistress's cocoa. Hokey later remembered putting something into the cocoa that turned out not to be sugar, but a lethal poison. The Ministry put it off to an accident given the fact that Hokey was old and probably confused. However, it is very likely that Tom Marvolo Riddle poisoned Mrs. Smith (in order to steal Helga Hufflepuff's Cup and Salazar Slytherin's Locket) and then magically changed Hokey's memory, with a Memory Charm, to make her look like the guilty party.

In a memory seen through the Pensieve, Harry Potter describes Hokey as "the tiniest and oldest house-elf [he] had ever seen". Her head did not reach the seat of Mrs. Smith's chair and she had papery-skin and wore a linen sheet as a toga.