The common tern was first described by Carl Linnaeus in his landmark 1758 10th edition of "Systema Naturae" under its current scientific name, "Sterna hirundo". The word "stearn" was used in Old English and a similar word was used by the Frisians for tern. "Stearn" appears in the poem "The Seafarer", written around 1000 AD. Linnaeus adopted this word for the genus name "Sterna". The Latin for swallow is "hirundo" and refers here to the tern's superficial likeness to that unrelated bird, which has a similar light build and long forked tail. This resemblance also leads to the informal name "sea swallow", recorded from at least the seventeenth century. The Scots names "picktarnie", "tarrock" and their many variants are also believed to be onomatopoeic, derived from the distinctive call. Due to the difficulty in distinguishing the two species, all the informal common names are shared with the Arctic tern.