penguinyoudaoicibaDictYouDict[penguin 词源字典]
penguin: [16] Penguin is one of the celebrated mystery words of English etymology. It first appears towards the end of the 16th century (referring to the ‘great auk’ as well as to the ‘penguin’) in accounts of voyages to the southern oceans, but no one has ever ascertained where it came from. A narrative of 1582 noted ‘The countrymen call them Penguins (which seemeth to be a Welsh name)’, and in 1613 John Selden speculated that the name came from Welsh pen gwyn ‘white head’.

Etymologists since have not been able to come up with a better guess than this, but it is at odds with the fact that the great auk had a mainly black head, and so do penguins. The earliest known reference to the word (from 1578) mentions the birds being found on an ‘island named Penguin’, off Newfoundland, so it could be that it was originally the name of the island (perhaps ‘white (i.e. snow-covered) headland’) rather than of the bird.

However, a further objection to this theory is that a combination based on Welsh pen gwyn would have produced penwyn, not penguin.
[penguin etymology, penguin origin, 英语词源]
penguin (n.)youdaoicibaDictYouDict
1570s, originally used of the great auk of Newfoundland (now extinct), shift in meaning to the Antarctic bird (which looks something like it, found by Drake in Magellan's Straits in 1578) is from 1580s. Of unknown origin, though often asserted to be from Welsh pen "head" (see pen-) + gwyn "white" (see Gwendolyn), but Barnhart says the proposed formation is not proper Welsh. The great auk had a large white patch between its bill and eye. The French and Breton versions of the word ultimately are from English.