adj.: Relating to syphilis, caused by it, or suffering from it.
noun: A person who has syphilis.
Etymology: Latin, lues, plague.
Lues was an old name for syphilis.
The name 'syphilis' was invented by Doctor Girolamo Fracastoro, in the early 1500s. Why he chose the name is unknown.
As far as I can tell, the name 'syphilis' predates 'lues' by about 100 years.