profligate (adj.)

1520s, "overthrown, routed, defeated, conquered" (now obsolete in this sense), from Latin profligatus "destroyed, ruined, corrupt, abandoned, dissolute," past participle of profligare "to cast down, defeat, ruin," from pro "down, forth" (see pro-) + fligere "to strike" (see afflict).

The main modern meaning "recklessly extravagant" is attested by 1779, via the notion of "ruined in morals, abandoned to vice" (1640s, implied in a use of profligation, an obsolete word attested from mid-15c. but first in a sense of "elimination, banishment"). Related: Profligately. As a noun, "one who has lost all regard for good principles," from 1709.