Correct spelling for the English word "Assumpt" is [ɐsˈʌmpt], [ɐsˈʌmpt], [ɐ_s_ˈʌ_m_p_t] (IPA phonetic alphabet).
There seems to be no specific word Assumpt in the English language. It is possible that you might be referring to the word Assumption. The etymology of Assumption traces back to the Latin word assumptio, which is the past participle of the verb assumere. Assumere is a combination of ad (meaning to) and sumere (meaning take or assume). Therefore, the etymology of Assumption can be understood as the act of taking to oneself or taking for granted.