Available
来自Big Physics
late Middle English (in the senses ‘effectual, serviceable’ and ‘legally valid’): from avail + -able. The sense ‘at someone's disposal’ dates from the early 19th century.
wiktionary
avail + -able
etymonline
available (adj.)
mid-15c., "beneficial," also "valid, effective, capable of producing the desired effect," from avail + -able. Meaning "at one's disposal, capable of being made use of" is recorded from 1827. Related: Availably.
