2: a person who stays around other people and uses them for personal gain
History for leech
Originally the English word leech meant “doctor.” Centuries ago doctors thought that a good way to cure sick people was to make them bleed. The blood of a sick person supposedly had harmful things in it that would flow away with the blood. To take bad blood out of sick people, early doctors often used little worms that suck blood. Leech, the word for a doctor, came to be used for these worms as well.
: any of numerous carnivorous or bloodsucking annelid worms that comprise the class Hirudinea, that typically have a flattened segmented lance-shaped body with well-marked external annulations, a sucker at each end, a mouth within the anterior sucker, and a large stomach with pouches of large capacity at the sides, that are hermaphroditic usually with direct development, and that occur chiefly in freshwater although a few are marine and some tropical forms are terrestrial — see medicinal leech