Wikipedia on Larus marinus, or the great black-backed gull:
The scientific name is from Latin. Larus appears to have referred to a gull or other large seabird. The specific name marinus means "marine", or when taken together, "sea gull".
Yeah but like, my dog is a dog but it's also a Labrador and also has a name. The great black-backed gull is also known as Larus marinus which means sea gull, and is also commonly referred to as a seagull. By what notion is that not a seagull?