Skittish (adjective)

1. Nervously high-strung.
2. Easily frightened.

Origin:

Late 17th century: from skittish, the past participle of obsolete skit "start, frisk", of unknown origin.

Examples:

1. The horse was skittish and would not let anyone near it.
2. She became skittish when he asked her to marry him.
3. The dog was skittish and ran away when we tried to pet it.
4. The skittish cat ran under the couch when we entered the room.
5. The skittish colt would not let anyone near it.