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Webster 1913 Edition

Verb.

[1st pref.

un-

arm

To disarm.

Sir T. Browne.

Verb.

To put off, or lay down, one’s arms or armor.

“I'll unarm again.”

Shak.

v.t. To disarm; to strip of armor or arms. [Not used. See Disarm.]

unarm ‎(third-person singular simple present unarms, present participle unarming, simple past and past participle unarmed)

To disarm, to remove the armour and weapons from.
- 1485, Sir Thomas Malory, chapter lxj, in Le Morte Darthur, book X:
  Thenne anone la beale Isoud sente in to the toune / and prayd syr Dynadan that he wold come in to the castel / & repose hym there with a lady / with a good wylle sayd sir Dynadan / & soo he mounted vpon his hors and rode in to the castel / & there he alyghte / and was vnarmed / & brought in to the castel