a·vail / əˈvāl/ • v. 1. (avail oneself of) use or take advantage of (an opportunity or available resource): my daughter did not avail herself of my advice.2. help or benefit: [tr.] no amount of struggle availed Charles | [intr.] the dark and narrow hiding place did not avail to save the fugitives. PHRASES: of little (or no) avail not very (or not at all) effective or successful: Latin was of little avail in the practical affairs of life.to little (or no) avail with little (or no) success or benefit: he tried to get his work recognized, but to little avail.

avail be of use or advantage. XIII. Native formation on †vail vb. (of equal date). — OF. valoir :- L. valēre be strong or worth; prob. after pairs like amount, mount.
So avail sb. XV; cf. AN. avail. Hence available XV.