Ran into ” parenchymal disassociation” on a medical research webpage, and googled it because I wasn’t sure what parenchymal meant. Lo and behold, the only exact matches for the phrase (5 or 6 of them) came from the same webpage. Proceeded next to “parenchymal”, and got the definition, then tried “parenchymal dissociation”. Result: hundreds of exact matches. So on and so forth ended with OED reference:
“dissociate” is from the Latin dissociare (to separate from fellowship). “Disassociate” was modeled after the 16th-century French verb désassocier.
Both words are recognized, and they mean the same thing. Dissociate saves a syllable and some hissing, so there seems little reason to follow the French. Today’s international news bolsters my skepticism:
France, having recently purchased $20.5 billion worth of new trains, now realizes that the trains will not fit into many regional stations. More hundreds of millions will be spent modifying station platforms. Transport Minister Frederic Cuvillier blamed an “absurd rail system” for the problems. “When you separate the rail operator from the train company,” he said, “this is what happens.”