Insulin

google

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early 20th century: from Latin insula ‘island’ + -in1.

wiktionary

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From Latin īnsula(“island”) (named for the islets of Langerhans, where insulin is produced) +‎ -in.

etymonline

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insulin (n.)

1922 (earlier insuline, 1914), coined in English from Latin insula "island" (see isle and compare insula); so called because the hormone is secreted by the islets of Langerhans in the pancreas. Insuline was coined independently in French in 1909.