The story
- Proto-Indo-European*slenk-
- Proto-Indo-European*slonk-ó-s
- Proto-Germanic*slangô
- Old High Germanslango
- Middle High Germanslange
- Yiddishשלאַנג (shlang)
- Middle High Germanslange
- GermanSchlange
- English todayschlong
Borrowed from Yiddish שלאַנג (shlang, “snake”; by extension, “a penis”) or German Schlange.
Etymology from Wiktionary, CC BY-SA 4.0.