Playfellow is compound of play (Old English plega 'play, sport') + fellow (Old English feolaga 'partner', from Old Norse felagi 'business partner'). Important recorded forms include plega (Old English) and felagi (Old Norse). Morphologically, the word preserves a built structure whose named elements carry the historical sense into English. The modern sense remains close to that composition, with the parts narrowing into a single lexical item. In current use it covers a companion in play; a playmate. The wider family includes related words such as play, fellow, and playmate.