The expression "dog days of summer" appears to derive from ancient Greek and Roman mythology according to which the star Sirius was indicative and probably responsible for the hottest days in summer:
- The ancient Greeks noticed that summer’s most intense heat occurred during the approximate 40-day period in the early summer when Sirius, the brightest star in the sky, rose and set with the sun. To them it was simple math. The daytime addition of the warmth of Sirius—ancient Greek for “glowing” or “scorcher”—to the blaze of the sun equaled extreme heat. According to Greek mythology, Sirius was the dog of the hunter Orion, and the ancient Romans placed the star in the constellation Canis Major (Latin for “Greater Dog”). The Romans thus referred to the sweltering period when the rising of the sun and Sirius converged as the “dies caniculares” or “days of the dog star.” (www.history.com)
The expression entered the English language in the 16th century:
- 1530s, from Latin dies caniculares, from Greek; so called because they occur around the time of the heliacal rising of Sirius, the Dog Star (kyon seirios). (etymonline).
The same expression remained similar to the Latin "caniculares" in other languages such as canicula in Portuguese, canicula in Spanish, canicola in Italian and canicule in French where the term has an older, medieval usage.
Was the term "canicola" used before "dog days" entered English common usage or was the expression unknown before the 16th century.
Was the expression imported or translated at that time by some some 16th century English writer?