If adults are using the term, it is not so much an insult as it is a way to tease them, as Dream Eater's answer suggests. As an idiom, both words are required to express the meaning. He is a scaredy cat is the correct usage of the phrase. If someone is shy, they may be hesitant to do an activity that causes fear. So yes, it could be used by someone to poke fun at the shy person.
Plainfield is a town in Guilford, Liberty and Washington townships, Hendricks County, Indiana, United States. The population was 27,631 at the 2010 census. Plainfield is located at 39Â°41â²51â³N 86Â°23â²5â³W / 39.6975Â°N 86.38472Â°W / 39.6975; -86.38472 (39.697471, -86.384672).
Established in 1850, Plainfield Township government serves the 80,000 residents in the Illinois villages of Plainfield, Joliet, Romeoville and Crest Hill. Plainfield Township's boundaries run to the North by 135th Street, to the South by Theodore Street, to the East by Gaylord Road and to the West by County Line Road.