first, a. (n.) and adv.
From Old English fyrst, fyrest, from common Germanic *furisto-, a superlative formation on the stem *fur-, for- (see FORE adv., FOR prep.).
From the same stem, with different superlative suffix, is formed Old English forma 'first,' whence the double superlative form fyrmest: see FORMER, FOREMOST.
The Proto-Germanic fur-, for-, represents Proto-Indo-European pr-, whence in most of the Indo-European languages words meaning ‘first’ are derived, chiefly with superlative suffixes. Compare Sanskrit prathama, Old Slavonic privu, Greek protos, proistos, Latin primus.