'baltic' (adj./n.) originates from Medieval Latin 'Balticus' and Latin 'Mare Balticum' referring to the Baltic Sea; the name for the sea likely comes from older Baltic or neighboring languages (possible connections include an Old Prussian or Baltic root and a Proto-Indo-European root meaning 'white' or 'shining'), though the exact origin is uncertain.

'balticus' in Medieval Latin and 'Mare Balticum' were used in medieval writings; the word passed into modern European languages and Middle/Modern English as 'Baltic', keeping reference to the sea and the region, and later developed the additional colloquial sense 'very cold' in English.

Initially it referred specifically to the sea or the region around it; over time it retained that geographic sense while English also developed an informal adjectival sense 'very cold' (chiefly British) derived from the cold climate associated with the region.