Many folks are named Randy nowadays. But at one time this must have solicited a snicker.
Randy’s been used as ‘lustful or lewd’ since the mid-1800s.
Horny’s been used to mean 'lustful or sexually aroused’since the 1880s, maybe as early as 1863.
bardos seems to be suggesting that the name “Randy” is recent. It isn’t - it’s short for Randall or Randolph.
Yeah, I was watching an episode of the TV show “Elementary” a while back and one character says to the protagonist, “Hi, I’m Randy.”, whereupon the protagonist asks, (I paraphrase) “Is that your name or are you referring to your state of sexual arousal?”.
I think the question is more when “Randy” stopped being used so much to mean sexual interest.
A discreet encouragement — ‘Everybody’s doing it’, and announcing some made-up famous couple choosing it for their baby in the cheaper celeb magazines — and we may get lower class morons to adopt Horny as a suitable name for their offspring.
I can’t decide if it’s better for a boy moron or a girl moronette.
“‘Randy Giles’? Why not just name me ‘Horny Giles’ or ‘Desperate for a Shag Giles’!”
I always think of “randy” as a British thing. Prince Andrew and all that.
“randy” is a Scottish word related to “rant”.
a lexicographer named Randall made the move to make horny more popular.
Suppose your name was “Randy Johnson” and they called you “the big unit”?
I would have thought the obvious answer would have been around puberty.
When I visited the US in 1976 I met various chaps named Randy and no Americans seemed to attach the connotation of “horny” to the name.
But what really made us Kiwis fall about in youthful giggles was constant references to “fanny”. As in a pat on the fanny. Forgive me - I’m chortling even now as I type. 
Well, you folks probably smoke fags and that would just be unthinkable here in the states. We wouldn’t even say it. 
The name “Randy” will still elicit snickers in Britain, where it is still used to mean highly sexed or sexually aroused, and rarely used as a name, the way it is in America. Did Americans ever use “randy” in this sense? I doubt it, given how freely it is used as a name.I do not know, but my guess is that “horny” originated in America, although its use has spread to Britain.
I presume “horny” was originally a reference to the erect penis sticking up like an animal’s horn. It seems odd to me that it has been appropriated to apply to sexually aroused women too.
In “My Secret Life”, written in the late 1800s, “horny” was hardly ever used.
You Kiwis (and Aussies and Limeys) are just built funny. Our fannies are behind, but yours are in the front. Somebody up there must have screwed up the blueprints.
“Randy”, as ouryL says in post #9, was originated as a Scots word meaning loud, rude, aggressive, and it comes from “rant”. By the early eighteenth century it had acquired the further meaning of boisterous, disorderly, wild, high-spirited, and by the late eighteenth it had started to develop its sense of lustful, sexually aroused - the first cite in the OED is from 1771. This is now the dominant sense.
“Horny” originally meant “consisting of horn”, and then it meant “horn-like”. It doesn’t acquire a documented sexual sense until the late nineteenth century - OED first cite is from 1889. It’s almost certainly from “horn”, which from the late eighteenth century had the slang sense of an erection. It was nearly always used in a verbal phrase - “to have the horn” or “to get the horn”.
The words are more or less interchangeable. It’s my impression that “horny” has long been the more-used word in American English, while “randy” was preferred in British English until comparatively recently, but may now be being eclipsed by “horny”.
Oh, all the time.
In the late 1980’s, when I was one person in a group of Americans working in England, we were told that anyone who usually went by the name Randy in the U.S. might consider going by Randall during the time that they were in England. The funny thing was that we knew that the word “randy” meant “horny.” Nobody in the U.S. was bothered by it though. Apparently, although the word “randy” is occasionally used in the U.S., it isn’t as common as it is in the U.K.