The bullseye, or bull's-eye, is the centre of a target (worth 10 points in target archery

Target archery

Modern competitive archery is governed by the World Archery Federation, abbreviated WA . Olympic rules are derived from WA rules. WA is the International Olympic Committee's recognized governing body for all of archery.Currently 142 nations are represented by WA archery governing bodies...

 or 50 points in darts

Darts

Darts is a form of throwing game where darts are thrown at a circular target fixed to a wall. Though various boards and games have been used in the past, the term "darts" usually now refers to a standardised game involving a specific board design and set of rules...

), and by extension the name given to any shot that hits the bullseye. In darts, a double bullseye is the centre (small) bullseye and counts as 50 points.

The word bullseye can therefore refer to any design or pattern featuring prominent concentric circles, visually suggesting an archery

Archery

Archery is the art, practice, or skill of propelling arrows with the use of a bow, from Latin arcus. Archery has historically been used for hunting and combat; in modern times, however, its main use is that of a recreational activity...

 target.

Consequently, "hitting the bullseye" became a term for an unexpectedly good success.

The logo for US Target Corporation

Target Corporation

Target Corporation, doing business as Target, is an American retailing company headquartered in Minneapolis, Minnesota. It is the second-largest discount retailer in the United States, behind Walmart. The company is ranked at number 33 on the Fortune 500 and is a component of the Standard & Poor's...

resembles a bullseye.