the word 'thrifty' has a journey from prosperity to frugality. it derives from the middle english noun 'thrift', which meant thriving, prosperity, or savings, itself borrowed from old norse 'þrift', a derivative of the verb 'þrífa' (to grasp, to thrive). the underlying sense is of something successfully grasped or acquired. the adjective-forming suffix '-y' (from old english '-ig') was added to mean 'characterized by thrift'. over time, the core meaning shifted from the state of being prosperous (having successfully saved) to the character trait of careful management that leads to that prosperity, giving us the modern sense of being economical and not wasteful.

Structure: thrift + y thrift (from middle english 'thrift', from old norse 'þrift', meaning prosperity, savings, related to the verb 'thrive') + y (from old english '-ig', an adjective-forming suffix meaning 'characterized by' or 'full of').