"one who asks questions or has doubts," early 15c., questiouner, agent noun from question (v.).Questionist is attested from 1510s.
Entries linking to questioner
question v.
late 15c., questiounen, "to inquire, ask, seek to know," from question (n.) and from Old French questioner "ask questions, interrogate, torture" (13c.), from question (n.). Hence "to dispute, doubt," by 1530s. Transitive sense of "inquire of by asking questions" is from late 15c. Related: Questioned; questioning. Alternative verb questionize is attested from 1847.