The story
From international scientific vocabulary, from insulin + de + glu + dec, an acronymically constructed postpositive modifier, reflecting "the same amino acid sequence as human insulin except for the removal of threonine in the position 30 of the B chain (Des-B30, "de") and the attachment, via a glutamic acid linker ("glu"), of a 16-carbon fatty diacid (hexadecanoic diacid, "dec") to lysine in the position 29 of the B chain."
Etymology from Wiktionary, CC BY-SA 4.0.