The only free and comprehensive online etymological dictionary of the Spanish language
asunto m. (Noun) "matter," "issue;" (plural) "affairs"
From Latin assumptus, the perfect passive participle of assumere "to take up," "to receive," from ad and sumere "to seize," "to undertake." Sumere is a contraction of Latin sub "under" (see so) and emere "to buy," but originally "to take." See also sumir. Emere is from Proto-Italic *em-e/o- "to take." From Proto-Indo-European *h1em-e/o- "to take."
Asturian asuntu, Portuguese assunto, Galician asunto, Italian assunto

"The ancients still knew that emo signified “take,” e.g. Festus: antiqui emere dicebant pro sumere (‘the ancients used to say emere for sumere “to take”’). There are etymological correspondences which confirm this: Lithuanian has imù ‘take’ and in Celtic, Irish has ar-fo-emat ‘they take’, where ar- and -fo- are preverbs. In Latin itself we have this sense in a series of compounds: demo ‘take away’, sumo ‘to remove’, promo ‘produce’ (‘draw wine’) etc. We should, therefore, note that emo first signified “take” and then “buy.”" ~ E. Benveniste, Indo-European Language and Society (1973)