Strong's Greek Concordance

G4315: προσάββατον

prosábbaton · “Friday”

Definition

a fore-sabbath, i.e. the Sabbath-eve

KJV translates it as: day before the sabbath

Word origin: from G4253 (πρό) and G4521 (σάββατον);

Extended definition

προ-σάββατον, -ου, τό
[in LXX: Psa.92:1-15 title. א (שַׁבָּת) שַׁבָּת) Psa.93:1-5 title., Jdth.8:6 * ;]
the day before the Sabbath: Mrk.15:42 (L, Tr., txt., πρὸς σ.).†
(AS)

Abbott-Smith Manual Greek Lexicon (1922) via STEPBible TBESG (CC BY 4.0).