'trial-level' originates from modern English as a compound of 'trial' and 'level'. 'trial' ultimately comes from Old French 'trier' (via Middle English 'trial'), where the root meant 'to try; to test or sort', and 'level' comes via Middle English from Old French 'livelle' (from Late Latin 'libella'), where it meant 'a small balance or instrument for measuring horizontality' (hence 'degree, plane, standard').

'trial' changed from Old French 'trier' into Middle English 'trial' and eventually modern English 'trial'; 'level' changed from Old French 'livelle' (and Late Latin 'libella') into Middle English 'level' and then modern English 'level'. The compound 'trial-level' arose in recent technical and scientific usage to denote measures or analyses at the scale of an individual trial.

Initially, 'trial' referred to the act of trying or testing and 'level' to a degree, plane, or measuring standard; over time their compound came to be used in scientific and clinical contexts to mean 'pertaining to the scale, data, or outcomes of an individual trial'.