The story
From blood + sucker. The “changeable lizard” sense is perhaps because of the reddish color of its neck.
First known use, by meaning
- from 14th c. An animal or insect that drinks the blood of others, especially by sucking blood through a puncture wound; a leech, mosquito etc.
- from 16th c. Someone who sheds blood; a bloodthirsty person; a violent criminal.
- from 16th c. Someone who preys on others, or who attempts to take as much from others as possible; an extortioner; a leech.
- from 18th c. A supernatural being who feeds on (especially human) blood; a vampire.
- from 18th c. Any of various lizards of the family Agamidae, especially the changeable lizard (Calotes versicolor) of Asia, and the jacky dragon of Australia, Amphibolurus muricatus).
Etymology from Wiktionary, CC BY-SA 4.0.