Fallacious, deceitful; now it means ill-tempered, carping. (Latin, captiosus.)
I know I love in vain, strive against hope; Yet in this captious and intenible sieve I still pour in the waters of my love.
Shakespeare: All's Well that Ends Well, i. 3.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894