A stalker is commonly referred to as:
- a person who harasses another person, as a former lover, a famous person, etc., in an aggressive, often threatening and illegal manner: Hollywood stars often have security guards to keep dangerous stalkers at bay. (dictionary.reference.com)
Stalker with the above connotation is a relatively recent term:
- Meaning "harass obsessively" first recorded 1991, probably from "pursue stealthily," Old English -stealcian, as in bestealcian "to steal along, walk warily," (etymonline)
The fact that the term usage is quite recent may be the consequence of a considerable increase of illegal harassment in the last couple of decades. I can imagine that stalkers, unluckily, were around well before 1991.
What was the common term used to refer to them or to their 'activity' before the term came into use presumably replacing previous definitions?
Were the terms stalker/stalking coined in a legal context (see the passing of anti-stalking laws below) or is there evidence that they were used in everyday language first?
As shown by @kristina Lopez California was the first State to pass anti-stalking laws:
California's stalking laws are most commonly associated with celebrity cases. In fact, celebrity stalking is what prompted the California Legislature to enact anti-stalking laws back in 1990.
The first was the repeated stabbing of actress Theresa Saldana. The second was the murder of actress Rebecca Schaeffer. In both cases, the defendants were obsessed fans who stalked the actresses. As a result of these cases,5 California enacted Penal Code 646.9 in 1990.6