تَحَتّمَ: وَجَبَ to be or become necessary, requisite, obligatory, mandatory, indispensable, imperative; to be inevitable, unavoidable, inescapable

تَحَتّمَ عَلَيْه: وَجَبَ عَلَيْه to be incumbent upon, be someone's duty, be imposed on

يَتَحَتّمُ عَلَيْهِ أنْ he has to, he should, he must, he ought to, it is his duty to, he is duty bound to