hebdomadal (adj.)youdaoicibaDictYouDict[hebdomadal 词源字典]
1610s, from Latin hebdomadalis, from hebdomas, from Greek hebdomas "the number seven; a period of seven (days)," from hepta "seven" (from PIE *septm; see seven) + -mos, suffix used to form ordinal numbers, cognate with Latin -mus. In later use as pedantic humor.[hebdomadal etymology, hebdomadal origin, 英语词源]