Knights Errant In France, from 768 to 987, the land was encumbered with fortified castles; in England this was not the case
till the reign of Stephen. The lords of these castles used to carry off females and commit rapine, so that a class of men sprang
up, at least in the pages of romance, who roamed about in full armour to protect the defenceless and aid the oppressed.

And the Knights Arrant were the ones who committed the rapes.

I remember learning the word "arrant" from R.L.Stevenson poem "My Shadow"
the last stanza being:


One morning, very early, before the sun was up,
I rose and found the shining dew on every buttercup;
But my lazy little shadow, like an arrant sleepy-head,
Had stayed at home behind me and was fast asleep in bed.