Dear Thomas,

> If not, what religious group/s at that time also used this word for
> its own monk?

See Jain Samana sutta:

parasamtavayakarana-vayanam, mottuna saparahidavayanam.
Jo vadadi Bhikkhu turiyo tasst du dhammo have saccam. (92)

A monk who avoids all speech that is likely to hurt others and speaks
only what is good to himself and to others observes the fourth virtue of
truthfulness. (92)

http://www.jainworld.com/scriptures/samansuttam9.asp

Rage dose ya do pave, pavakamma pavattane.
Je bhikkhu rembhai niccam, se na acchai mandale. (130)

The two sins attachment and aversion lead one to commit sinful acts.
That monk who always besieges them will not wander in this mundane
existence. (130)

http://www.jainworld.com/scriptures/samansuttam10.asp

No sakkiyamicchai na puyam, na vi ya vandanagam kuo passamsam?
Se samjae suvvae tavassi, sahie ayagavesae sa bhikkhu. (234)

he who desires no honour, no worship, no salutation even, how will he
desire praise? He who has self-control, observes the vows correctly,
practises penance and seeks to know the true nature of the soul is the
real monk. (234)

http://www.jainworld.com/scriptures/samansuttam18.asp

Sayanasanathane va, je u bhikkhu na vavare.
Kayassa viussaggo, chattho so parikittio. (480)

A monk who makes no movements of his body while sleeping, sitting or
standing and checkes all activities of his body is said to observe the
sixth penance of bodily steadines. (480)

http://www.jainworld.com/scriptures/samansuttam28.asp

Best wishes,

Dmytro