asseverate

1. (transitive) To assert earnestly, seriously, and confidentlyExamples: "Whereas Your Maiesty hath received true information of great sums of Money endeavoured to be borrowed of Your City of London, by directions proceeding from both Houses of Parliament […] (I Your Maiesties faithfull Subiect) doe conceive, and dare asseverate, that it is intended upon no other pretence then for the Honour and defence of Your Maiesty,"; "I will myself asseverate and bind it by an Oath, that the Muff thou bearest in thy Hand belonged unto Madam Sophia;"; "“And I presume you can also asseverate to his worship, that no man is better qualified than I am to bear testimony in this case, seeing that I was by you, and near you, constantly during the whole occurrence?”"transitive