Most cats scare easily or "jump" as soon as they hear noise or sense movement. When we call someone a "scaredy-cat" it means that person get scared easily or is afraid of something.
(1) "You're afraid of thunder? You're such a scaredy-cat!"
(2) "Tracy went camping all by herself. She's definitely not a scaredy-cat"
(3) "My son is too much of a scaredy-cat to skip class."
Although "scaredy-cat" means something, the word "scaredy" can never be used on its own as it doesn't have any meaning when used by itself.
Do you think you're a scaredy-cat?