*kreus-

1806, from French croûton "small piece of toasted bread," used in soups, salads, etc., from croûte "crust," from Old French crouste (13c.), from Latin crusta "rind, crust, shell, bark" (from PIE root *kreus- "to begin to freeze, form a crust").

early 14c., "hard outer part of bread," from Old French crouste (13c., Modern French croûte) and directly from Latin crusta "rind, crust, shell, bark," from PIE *krus-to- "that which has been hardened," suffixed form of root *kreus- "to begin to freeze, form a crust." From mid-15c. as "any hard, external portion of comparative thinness;" meaning "outer shell of the earth" is from 1550s.