From Old English 'brægen,' uniquely West Germanic — it has no cognate in German (which uses 'Gehirn'), surviving only in English and Dutch.
The organ of soft nervous tissue contained in the skull, functioning as the centre of the nervous system.
From Old English 'brægen' (brain), from Proto-Germanic *bragną (brain), possibly from PIE *mregʰ-mn- (skull, brain), related to Greek 'brekhmos' (βρεχμός, front part of the head, top of the skull). The word is primarily West Germanic — it appears in Old English, Old Frisian 'brein,' and Middle Low German 'bregen,' but not in Gothic or the North Germanic languages, which used different words (Old Norse 'heili,' related to 'whole'). This restricted distribution suggests the word may be a West Germanic innovation or a borrowing
German uses 'Gehirn' (not a cognate of 'brain') for the organ. The English word 'brain' has no cognate in German, Gothic, or Old Norse — it's a distinctly West Germanic word that survived only in English and Dutch/Low German. Most European languages use words derived from other roots entirely.