The story
From obsolete/dialectal sheld (“variegated”) + duck. Compare typologically Russian пега́нка (pegánka) (< пе́гий (pégij)).
Etymology from Wiktionary, CC BY-SA 4.0.
shelduck
shel·duckToday it means: Any of various waterfowl of the genus Tadorna, native to Eurasia, Africa and Australasia. Full definition →