"economical" is a different word than "economy", and also "affordable" or "thrifty", while a related concept to either the original sense of "economy" in Englis

"economical" is a different word than "economy", and also "affordable" or "thrifty", while a related concept to either the original sense of "economy" in English from the 15th C or the even older Greek root (the two are different) is not either off those simply transformed from a noun to an adjective without other shift of meaning.