Question: what is the meaning of the idiom to no avail?
Answer: Also, of little or no avail. Of no use or advantage, ineffective, as in All his shouting was to no avail; no one could hear him, or The life jacket was of little or no avail. This idiom uses avail in the sense of “advantage” or “assistance,” a usage dating from the mid-1400s. Also see to little purpose.