Streymoy (Danish: Strømø) is the largest and most populated island of the Faroe Islands. The name means "island of currents."
Navigatio Brendani 11.2:
vīdērunt aliam īnsulam, prope sibi iūnctam, interveniente fretō nōn magnō.
The "other island" is perhaps Streymoy, separated from Vágar by only a narrow strait.