Per Wikipedia: Mentholatum Deep Heating Rub (branded as "Deep Heat" outside of the United States)

As a midwestern American born in the early ’70s, I have never heard the term "deep heat" in my neck of the woods.

Deep Heat as a brand name is specifically a British/Australian thing.

There is the eternal debate about the alleged Britishness of saying "salt beef"; Americans typically say "corned beef."

Gilbert & Sullivan, of course, were British.

(Edit: my info is outdated, Deep Heat was actually sold here before my time.)

On Ancestry.com newspaper there is between the years 1955-1975
6,041 hits in USA on "Deep heat" and they seems all to be ads for;

"DEEP HEAT from new mentholatum rub"
or
Different massage devices.

There is also a derby horse in California named "Deep Heat" (in the 1960s/1970s)

And…

Zodiac Killer’s "Little List letter", were he used "deep heat", was postmarked June 26th 1970.
And same month and year, June 1970, Ancestry.com newspaper show 107 "Deep heat" hits in California newspapers.

Quote from the June 26, 1970 "Little List letter" :

" Others will hang by their thumbs + burn in the sun
then I will rub them down with deep heat to warm them up.

OK, I will concede: "Deep Heat" WAS sold here — in the 1950s. By the 1960s, I only see references to "Deep Heating" (though papers would shorten it to "Deep Heat"). I know I looked into this topic before, but it must’ve been longer ago than I thought.

When you talk about pain lotion (and I assume that’s what Zodiac’s referring to, but who the heck knows with him), Americans will generally think "Bengay," which has been around forever. Bengay is the butt of many an old man joke.

Does anyone have grandmas or grandpas who use "deep heat" as a catch-all term for this stuff?

I’m English,56 now,only know corned beef as corned beef.salt beef must be an older term.my dad,born 1922,only ever called it corned beef.my guess is that if the zodiac was into Gilbert and sullivan he may have read some English literature,possibly older stuff,and picked up some outdated words and phrases.even as a kid,I don’t remember many people using shall,definitely older usage.deep heat always means the brand over here(be careful where you put it,guys!!!!!)

Lots of stuff like that back then, "deep heat" could mean a number of products with different names: https://www.youtube.com/watch?v=OAEJTcdIUqU

https://www.youtube.com/watch?v=O5Cd0WffvfM
Deeeeep heeeeat / gooooood byyyyyeee

Sort of creepy

Up here, we refer to soda as pop…and others refer to pop as Coke, no matter which brand it is.

But a quick Google shows that people have been debating "salt beef" and "deep heat" for years. I suppose you could argue that Zodiac didn’t capitalize the D and H.

That video, though…wow.

Here in Newfoundland, Canada we eat salt beef every Sunday. And we refer to it as “salt beef”. He very well may have some ties to Canada lol. Only god knows

Edit: and we have been for eons

The so called "Britishisms" in the Zodiac letters go much deeper than most people, even experienced researchers, realise. The letters are chock full of them. Unfortunately for the OP, I am an incredibly lazy individual, so I won’t take the time to list all of the examples, but suffice it to say the list of American expressions would probably be shorter. There’s a Zodiac book out there somewhere in which the author lists each example in exhaustive detail, and once highlighted, it cannot be unseen. I suggest just reading the letters for yourself and making notes, you won’t have to look hard.

As for salt vs. corned beef, to my ears that does ring more archaic to my ear. Corned beef I’m sure has been universally the popular term since the turn of the century, but I recall vividly that characters in Robert Louis Stevenson books seemed to subside on nothing but salt beef. Salt beef was a common ration for the navy and features as the primary means of sustanaince for many great heros of exploration and adventure novels from the 18th and 19th century. The association with heroism and exploration was strong enough that Hugh Lofting revived it as a trope in the 20’s. I’m sure half the hero’s of old comics and adventure stories subsided on it to. It’s a bit like invisible ink in Nancy Drew, or The Smugglers of Smuggler’s Cove in an Enid Blyton novel, the smugglers in question of course subsiding on nothing but salt beef.

So what does it all mean? It’s impossible to say, it could mean he wasn’t born in the USA, or that he was older, or raised by older parents, or nearly anything. My own speculative theory, after the preponderance of evidence in the letters as a whole and his other interests is this, I believe the Zodiac used Bristisims because he was pretentious. In other words, a pseudo-intellectual wanker. Think about it, he seemed interested in comics, old films, detective novels, musical theatre and the characters in many of the works he referenced had personas which included overly formal speech. Think of the Count in The Most Dangerous Game. Zodiac was persona, if he went to bother of making a costume, it’s not surprising he would give the character a style of words, and the style he chose was the overly formal manner of a classic super-villain. Supervillains talking in Briticisms is a recognisable trope still used down to this very day.

Speaking of Canada, I did spot an ad for Deep Heat in a Canadian newspaper circa 1969.

BTW, the "Deep Heating" product I’m referring to had an almost identical logo to Deep Heat; I’m not sure if it was a name change or a clone product. But it was frequently shortened to "Deep Heat" in ads.

Still seems like a strange thing to shoehorn into a sadistic rant. What kind of men would have "deep heat" on the brain? Maybe older guys and athletes. As a non-athlete, I didn’t start having "aches and pains" till my 40s. But yes, that there’s an overall pattern of trying to "sound British" or maybe just archaic, is hard to deny. "Drownding" is another one.

Despite the suggestions of some British background, none of those who heard his voice detected any accent.

Well, I’ve assimilated a lot of British culture, myself. I’ve never set foot over there.

Well, I’ve assimilated a lot of British culture, myself. I’ve never set foot over there.

Me too. Assuming Monty Python and Benny Hill constitute culture.

https://youtu.be/Do6ZaBcdCoU