misreckoning
/ˌmɪsˈrɛk(ə)nɪŋ/ /ˌmɪsˈrɛk(ə)nɪŋ/noun
Incorrect reckoning or calculating of accounts; (more generally) miscalculation; an instance of this.
Origin
Mid 16th century; earliest use found in John Palsgrave (d. 1554), teacher and scholar of languages. From misreckon + -ing.