The story
- Proto-Germanic · derived from*swankaz“lithe, bendsome, slender”
- Proto-Germanic · inherited from*swankijaną“to cause to sway, swing”
- English todayswank
From dialectal swank (“to strut, behave ostentatiously”), perhaps from an unrecorded Old English root, derived from Proto-Germanic *swankijaną (“to cause to sway, swing”) or from Proto-Germanic *swankaz (“lithe, bendsome, slender”), related to the Scots swank and the Middle High German swanken, modern German schwanken (“to sway”).
Etymology from Wiktionary, CC BY-SA 4.0.