Hey Glo,
I had never noticed that before. Interesting.
See... I usually associate the Devil with (amongst other things) a connection to the Earth... to something that we know is bad for us: whether that be through addiction, too much hedonism and thus neglecting of various other emotional or spiritual values. Capricorn as an Earth sign and its appearance on the Devil's hand is thus very useful in understanding this.
Capricorn, is actually capricornus, which literally stands for 'horned goat'.
According to this web-site:-
http://www.stariq.com/Main/Articles/P0001903.htm
'Capricorn is often depicted as the "sea goat" from the myth of Pan, the horned woodland god of goats and shepherds. The bearded and "horny" Pan was one of the satyrs, half-human and half-beast, known for their voracious sexual appetites (origin of the word "satyriasis"). According to one version of the myth, Pan, fleeing from the beast Typhon, jumped into a river just as he was transforming himself into a fish. The lower half of his body became fishlike, but his upper body above the water remained in the form of a goat.
Modeled after the myth of Pan, the devil in medieval times was depicted with the horns and hooves of a goat. Our word "panic" comes from the reaction of Pan's nursemaid when she beheld his horned skull and ugly bearded face as he emerged from the womb. She ran away in a fright—the first "panic" in recorded history.'
Interestingly, that same web-site points out Capricorn's relation to the Winter Solstice. Apparently, the day of the Winter Solstice is one of the darkest in the whole year. Perhaps this can also be drawn upon in our understanding of the Devil card, perhaps reflecting 'dark-times'.
C