Deriving from ‘have to’, or ‘have+{infinitive}’ broken down into ‘have+to+{
verb}’ but minus the
verb, ‘hafta’ works as a
verb-modifying adverb taking the place of the modal-auxilary ‘must’ which means
literally ‘to be required to __’. In colloquial speech (as opposed to ‘formal speech’ under which you would not
use this word{hafta}}, it means simply to have a strong desire towards, or want for, doing {something}, with the ‘something’ usually
seen through the eyes of the speaker as a *necessity* (even if in actuality it is no more than icing on the cake).
Synonyms: haveto, have to, must, ’ve to, oughtta{ought to}, wanna\wanta{want to}, gotta{got to}
See also: musta\must’ve(must have..not nonsensical ‘must of’), shoulda\should’ve{should have..not nonsensical ‘should of’}, ta\tta, -ta\-tta, t‘be