The story
- Hawaiian · calque ofkī hōʻalu“loosen the [tuning] key”
- English todayslack-key
From a translation of the Hawaiian kī hōʻalu (“loosen the [tuning] key”).
Etymology from Wiktionary, CC BY-SA 4.0.
slack-key
Today it means: (of a string instrument or a manner of playing one) Performed with loosened strings, such that all of the strings play in the same key (most often G major). Full definition →
Hawaiian kī hōʻalu