For many years I've been subject to a particular variety of slip of the tongue which as far as I know is an as-yet unobserved and unnamed phenomenon.
The situation is this: There are two words that have essentially the same meaning, and so your mind is unable to choose between them. Instead of one or the other, out comes a mishmash that combines half of each, which just happens to be another, quite unrelated word. Awkwardly, you grasp for the correct term--and instead produce a second mishmash with the remaining elements, which turns out to be yet another unrelated word.
The first time it happened was when I was much younger, driving about with my siblings, and observed a heavy-set woman working in front of her house. "There's someone working in her lard," I said, and then on further reflection corrected, "No, no, I mean her yawn!"
When I first studied corporate law, I spent a lot of time pondering what exactly happened when a corporation issued shocks--er, that is, stares.
And recently I was telling DOB about how the children went out in the puddles and got their shoots--that is, their booze--soaping, that is, socking, wet.
So I propose a term for this phenomenon: a synacism. Have you ever met one?