A landlubber is someone who has no knowledge of boats or the sea. According to sailors, pirates, or anyone who permanently lives on a boat, all us land dwelling people can be referred to as "Landlubbers." The etymology of landlubber is from the combination of "land" and "lubber." Lubber (noun) referring to a clumsy, lazy, or all around inexperienced person with boats or nautical knowhow. Usage in a sentence:

"Ye landlubbers couldn't tie a knot to save yer lives!"