Where does “σαββατικός” come from?

σαββατικός (Ancient Greek) comes from Hebrew שַׁבָּת, from Akkadian šapattum — 15.

Ancestry of “σαββατικός”, step by step

Step	Language	Word	Meaning
1	Hebrew	שַׁבָּת	Sabbath, Shabbat; weekly day of rest; sabbath
2	Akkadian	šapattum	15