While he was once named as Tadatsune by his father Yorinaga in 1145, his name was changed to Kanenaga on the following day due to his grandfather Tadazane FUJIWARA's strong opposition.
久安元年（1145年）に、父頼長より「忠経」の名を与えられるが、祖父藤原忠実の強硬な反対により翌日兼長と改められた。