Obligatory is a word; obliged is a word. It would appear obligated is an adjective in biology meaning “Able to exist or survive only in a particular environment or by assuming a particular role”. Obligate as a verb (To obligate him) is a backformation from obligatory, originally by poorly educated people who didn’t realise it was related to ‘obliged’–then it filtered into everyday American speech. The OED records its first usage in 1533, and it’s notable that it’s use mainly by a) people who spelled wackily all the time anyway and lived hundreds of years ago and b) Americans.
I maintain that since the language’s name (English) comes from England, and not America, our version of it is the default, the least adulterated, and the most superior. Central–>Centre, not Centeral–>centre. And so on.
But that’s just me being an imperialist snob.
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