The story
- Proto-Indo-European*h₁es-
- Proto-Germanic*sunjō
- Proto-West Germanic*sunnju
- Old Englishsynn
- Old Englishsynniġ
- Old Englishsyngian
- Middle Englishsyngen
- Middle Englishsynnen
- Middle Englishsynnere
- English todaysinner
From Middle English synnere, equivalent to sin + -er. Compare Saterland Frisian Säänder (“sinner”), West Frisian sûnder (“sinner”), Dutch zondaar (“sinner”), German Low German Sünder, Sünner (“sinner”), German Sünder (“sinner”), Danish synder (“sinner”), Swedish syndare (“sinner”), Icelandic syndari (“sinner”).
Etymology from Wiktionary, CC BY-SA 4.0.