Krastiņš is a Latvian surname that traces its origin to the Latvian word krasts, meaning “shore, coast,” combined with the diminutive/patronymic suffix -iņš. The surname thus likely arose as a toponymic or descriptive name for someone who lived by a shore or coast.
In Latvian naming practices, the suffix -iņš is commonly used to form patronymic surnames (son of) or diminutives. The feminine equivalent of Krastiņš is Krastiņa. As a class, these types of surnames in Latvia typically emerged during the 19th-century surname reform and after the abolition of serfdom in 1817–1819, when many Latvians were required to adopt fixed family names for civil registration.
While Krastiņš does not have a high frequency relative to common global surnames, it is distinctly Latvian and can be found across Latvian diaspora communities worldwide.
Feminine Forms
Sources: Wiktionary — Krastiņš