It refered to the group (or member) who divided a day into six parts and kept practicing nenbutsu (Buddhist invocation), and they usually used kenmitsu-jiin (exoteric temples of Esoteric Buddhism) since the group had been formed.
一日を6分割して不断念仏する集団（ないし成員）を指し、古代以来、顕密寺院にいた。