This site claims that the word came into usage in the 1960s. If it did, it caught on fast. I recall it in common usage among kids by 1965.
Also, is there a name for this kind of word that has something of the sense of onomatopoeia, but is not referring to a sound? It just seems to me to be a very good description of someone or thing even if you didn’t know it’s meaning.
Hard to believe people hadn’t been dipping shit since time immemorial. Especially when there were still so many outdoor facilities.
I would have guessed that it morphed from “dumbshit.”
rapidly was upped to ‘double dipped’
I assumed it came by similarity to dipstick, which is also slang for a stupid person.
And I always thought dipstick was an attempt to suggest dipshit without saying shit.
According to the OED:
Further research indicates:
Nah, a dipstick is a stick that you dip into things. The most common variety probably being for checking your oil at the gas station.
There was a recent thread in which someone showed the result when Google Ngram was applied to the phrase “the whole nine yards.” I decided try it for “dumbshit” and “dipshit.” I didn’t bother with “dipstick,” since that has another meaning that isn’t relevant and which probably accounts for most of the uses of the word. Here’s the results:
As you can see, it appears that “dumbshit” first was recorded in print in about 1958 and “dipshit” in about 1963.
True, but that doesn’t mean it wasn’t used as a euphemism, something the OED confirms.
Thanks. It really does take off in the 60s. Seems like such a good word, I’m surprised it wasn’t around longer.
“Dipstick” was commonly used by Del Boy (to describe his brother Rodney) in the BBC series Only Fools and Horses in the 1980s. See also “plonker”. 
Terminator 2 has a hilarious scene in the “Safe for Network TV” cut where Ed Furlong has the obscene version substituted out for the “mild” one.
What is the source of the apparent usage in 1900 for the “dumbshit” search ? Bad data perhaps ?
I don’t know.
When I was an adolescent in the Baltimore, it was a source of never-ending fun that the name Dikshit was in the phone book.
What a dipshit for not getting an unlisted number.