means A seagull is any of various seabirds in the gull family, typically white and grey, known for loud cries, coastal living, and a fearless willingness to steal your chips.

from From "sea" + "gull," the bird-word "gull" arriving in English in the late Middle Ages, probably borrowed from a Celtic source — compare Welsh "gwylan" and Cornish "guilan," likely echoing the bird's wailing call. The same root may underlie the insult "gull," meaning a dupe or easy mark, though here it's the bird doing the robbing rather than being robbed.