1: σάββατον
(Strong's #4521 — Noun Neuter — sabbaton | sabbata — sab'-bat-on )

the latter, the plural form was transliterated from the Aramaic word, which was mistaken for a plural; hence the singular, sabbaton, was formed from it. The root means "to cease, desist" (Heb., shabath; cp. Arab., sabata, "to intercept, interrupt"); the doubled b has an intensive force, implying a complete cessation or a making to cease, probably the former. The idea is not that of relaxation or refreshment, but cessation from activity.

Exodus 31:16,17Exodus 20:8-11Matthew 12:9-13John 5:5-16Mark 1:32Matthew 12:1Mark 2:23Luke 6:1Mark 2:27Colossians 2:16Hebrews 4:4-11Romans 14:5Galatians 4:9-11Matthew 12:1,11Matthew 12:5 Matthew 12:224:20Mark 6:2Luke 6:1 John 9:14 Matthew 12:2Acts 16:13Matthew 28:1LATE. ONE
2: προσάββατον
(Strong's #4315 — Noun Neuter — prosabbaton — pros-ab'-bat-on )

signifies "the day before the sabbath" (pro, "before," and No. 1), Mark 15:42; some mss. have prin, "before," with sabbaton separately).