Tico is a colloquial name for the natives of Costa Rica.
Costa Ricans usually refer to themselves as ticos instead of using the more-formal costarricense. Some dictionaries show the formal name as costarriqueño, however this is never used in practice in modern Spanish.
The word tico derives from the tendency of Costa Ricans to use the -ico diminutive suffix in Spanish instead of the more common and widely-used -ito. A decline in the use of the former has been occurring over about the last twenty years in Costa Rica, though it remains relatively common.
