One hypothesis for the original function of precursors of charged trna is that

tRNA-precursors were smaller than the modern tRNA and their primary function was to participate in the formation of new structures by joining two or more RNA molecules.

The adaptor hypothesis is the explanation of how information could be extracted from a nucleic acid into a string of amino acids in a specific sequence. The proposed explanation involved recognition between the adaptor (today tRNA) and the template nucleic acid.