***** dog days plural noun 1. the hot period of the summer reckoned in ancient times from the  heliacal   rising of Sirius (the Dog Star) 2. a period marked by inactivity[source] Word Origin C16: translation of Late Latin diēs caniculārēs, translation of Greekhēmerai kunade …1530s, from Latin dies caniculares, from Greek; so called because they occur around the time of the heliacal rising of Sirius, the Dog Star ( kyonseirios). Noted as the hottest and most unwholesome time of the year; usually July 3 to Aug. 11, but variously calculated, […]