Is it farther or further?
c.1400, nome, "deprived of motion or feeling," literally "taken, seized," from past participle of nimen "to take, seize," from Old English niman "to take, catch, grasp" (see nimble). The extraneous -b (to conform to comb, limb, etc.) appeared 17c. The notion is of being "taken" with palsy, shock, and especially cold. Figurative use from 1560s.
1550s, from numb (adj.). Related: Numbed; numbing.
Being unable or only partially able to feel sensation or pain; deadened or anesthetized.
Being emotionally unresponsive; indifferent.
Stupid; unresponsive (1950s+)