Oh, Fell Felon!
A felon is someone who has committed a felony, a serious crime with serious consequences. The class includes acts such as murder, rape, burglary, or treason. In early English law, it was cause for losing one’s fee--the land granted to a vassal by his lord. Punishment might additionally include an amputated limb or even execution.
While there is some uncertainty, the OED seems to lean towards an Old French/Latin word meaning “someone full of bitterness, venom, or gall.” It would then have a connection to the adjective fell--fierce, savage, cruel, ruthless:
"Wide wounds emongst them many a one he [Sidney] made,
Now with his sharp borespeare, now with his blade...
So as he rag'd emongst that beastly rout,
A cruell beast of most accursed brood:
Vpon him turnd (despeyre makes cowards stout)
And with fell tooth accustomed to blood,
Launched his thigh with so mischieuous might,
That it both bone and muscles ryued quight".
Spenser’s Astrophel (1595)
The word fell survives in the popular saying “one fell swoop,” originally a grim reference to a hawk or other bird of prey swooping down on its victim. Less menacing in our day, it now means “all at once.”
Felon as an adjective has generally referred to negative qualities:
• terrible, wicked, and base (1300)
• murderous (1320)
• angry or sullen (1374)
• stolen (1631)
On the other hand, it mysteriously acquired a positive connotation at times, possibly because some cruel qualities were an asset for warriors:
• brave, courageous, and sturdy (1375)
• tremendous, huge, or terribly great (1450)
Felon , n. 2, is connected through the Latin word for gall, but it refers to an abscess, an inflamed sore, a boil, or a suppuration.
SIDEBAR: Felony, a Swiss Melodic Metal Band
(substitute @ for AT above)