The custom became popular, but it has no certain history or origin and could be called the product of what we now call commercialism; like chocolate on St. Valentine's Day, or 'eho-maki' (rolled sushi that is said to bring luck when eaten in 'eho' [the lucky direction]) on 'Setsubun' (February 3).
鰻を食べるのが主流となったのは確固とした由緒由来が有るわけではなく、バレンタインデーのチョコレートや節分の恵方巻きなどと同様、現代でいうコマーシャリズムの産物といえよう。