Where does “Allen key” come from?

Allen key (English) comes from English key, from English cay, from Spanish Cayo, from Taíno cayo — small island.

Allen key (English): A hex head wrench

Definitions

  1. A hex head wrench

Ancestry of “Allen key”, step by step

Allen key traces back through two separate lines of ancestry.

via English key

StepLanguageWordMeaning
1EnglishkeyAn object designed to open and close a lock; An...
2EnglishcayA small, low island largely made of sand or coral
3SpanishCayokey island
4Taínocayosmall island

via English Allen

StepLanguageWordMeaning
1EnglishAllenShort for Allen wrench
Every word from Taíno cayoEvery word from Spanish CayoEvery word from English cay
Allen key — Etymology, Origin & Word History | Etymology Explorer