Like so many slang or dialect words of previous generations, this one is now very rarely encountered. It gained some publicity in 2011 through being listed by the publishers of Chambers Dictionary as a word with a pleasing sound.
When it appeared in the language — in the middle of the seventeenth century — it was a sadly incompetent attempt to say intoxicated, perhaps under the influence of drink (“I’m not so tosticated as you think I am”). An influence may have been the even older tosspot, a person who habitually tossed back his pot of drink, hence a heavy drinker or drunkard.
I fancy thou art a little intoxicated tonight. Tosticated! Tosticated! I scorn your words, cries Deborah. I defy the best man in Bath, to say black is my eye; or that I was ever consarned in liquor, since my name was Deborah. Tosticated! No; God help me! I have drunk nothing to-day, but a little tea for breakfast, and half a pint of ale at my dinner.
The Spiritual Quixote: or, the Summer’s Ramble of Mr. Geoffry Wildgoose, by Richard Graves, 1773.
Rather later, the symptoms of that state became confused — under the influence of the first syllable of the word perhaps — with those of being tossed about, and took on the idea of being perplexed or distracted.
Variously spelled, as tossicated or in other forms, recorders of English dialect near the end of the nineteenth century found it to be widely distributed, from Cumberland and Yorkshire down to Somerset and Devon. But by then it had vanished from the printed word. Chambers is the only British dictionary that continues to include it.