on one's say-so

on one's say-so

According to one's authority, as in I'm reorganizing the files on the boss's say-so, or You can skip the exam? On whose say-so? The noun say-so, dating from about 1630, originally meant simply "saying something," that is, an assertion (without authority or proof). By the early 1800s it had acquired its present meaning.
See also: on