1670s, "capable of being performed or affected," from French pratiquable (1590s), from pratiquer "to practice," from Medieval Latin practicare "to practice," from Late Latin practicus, ultimately from Greek (see practical). By 1710 as "capable of being actually used."
Possible notes that which may or might be performed if the necessary powers or means can or could be obtained ; practicable is limited to things which may he performed by the means that one possesses or can obtain. [Century Dictionary]