Just curious.
Ketchup
Since it’s a word taken from the Chinese, and the original sounds like “ketchup”, and it was originally spelled “ketchup”, I have to go with that one. I don’t know where “catsup” came from. The only time I’ve heard it pronounced was on a Del Monte commercial.
I think “catsup” needs to go the way of the misguided “hiccough”.
You can find old references to it also spelled “catchup.” Maybe “catsup” was an attempt to Wade-Giles it?
ETA: A search on this message board reveals 14 pages of “catsup” going back to 2001, and 30 pages of “ketchup” going back only to 2009.
I thought it came from a Malay word – the Indonesian word “kecap” is related – though there are similar words in Chinese dialects that may be cognate. However, “catsup” does seem to be an attempt to make it spell like some unrelated English words.
Even the Perfect Master doesn’t know. (How come they call it “ketchup” sometimes and “catsup” other times?)
Unless your Homer Simpson who LOVES CATsup but hates Ketchup 
Whenever someone says catsup, I think of Mr. Burns at the grocery store. 
I grew up in Heinz territory in western Pennsylvania, so to me, it’s always been “ketchup.”
What about the Burn’s O’s?
You know this thread needed a poll
Ketchup, and however you spell it, it’s a vile smelly goop.
IMO.
Dad pronounced it ‘cats-up’. ISTR it being called ‘Catsup’ on the bottles we used at home (late-'60s through the '70s). So I say and spell ‘catsup’.
‘Ketchup’.
Calm down. Here, have a doughknot.
Old friend of mine always pronounces it Cats-Up. Only person I’ve ever know that did this.
The earliest spelling cited in the OED is “Catchup”, in 1699.
Mustard.
Is that something like moutarde?
**Ketchup or Catsup? **
Yes.