“Do not have fasting days with the hypocrites. For they fast on the second day from the Sabbath and the fifth. You should fast on the fourth and sixth.”
Αἱ δὲ νηστεῖαι ὑμῶν μὴ ἔστωσαν μετὰ τῶν ὑποκριτῶν. νηστεύουσι γὰρ δευτέρᾳ σαββάτων καὶ πέμπτῃ· ὑμεῖς δὲ νηστεύσατε τετράδα καὶ παρασκευήν.
From the Oxford English Dictionary. s.v. “Monday”
Monday, n. and adv.
Compare ( < post-classical Latin Lunis dies ) Old French lunsdis (1119; c1160 as lundi ; French lundi ), Old Occitan diluns , dialus (15th cent.), Catalan dilluns (14th cent.), Spanish lunes (13th cent.), Italian lunedì (1282)