Caiside is an Irish given name derived from a byname meaning "curly haired", from Irish cas "twisted, curly". It is historically a surname, anglicized as Cassidy. The modern use as a first name in Ireland is uncommon but has heritage roots. Notable bearers include mythical or medieval figures from Ulster Cycle tales, where a warrior or poet named Caiside appears. The name is concentrated in Irish-speaking areas and among the Irish diaspora.