Much more common in first and second person singular (“I wanna”, “you wanna”) than in third person singular or (first or third person) plural affirmative (“he wanna”, “she wanna”, “we wanna”, “they wanna”), and subjectively judged as flatly incorrect for third person, and marginal in plural. However, all forms find some use, particularly in song lyrics.
Rejection of third person singular affirmative *“he wanna” and *“she wanna” can be explained by “want to” reducing to wanna, but “wants to” not doing so, instead being pronounced approximately as “wants ta”. This objection does not arise in the negative (“he doesn’t wanna”, “she doesn’t wanna”), due to the absence of -s in the negative: “he does not want to”, “she does not want to”, and these forms are both common and unobjectionable. First and third person plural affirmative is also quite uncommon and somewhat objectionable, with the negative forms being very common, without an apparent explanation.
Old High German