1535-45; < Latinplausibilis deserving applause, equivalent to plaus(us) (past participle of plaudere to applaud) + -ibilis-ible
plausibility, plausibleness, noun
1. Plausible, specious describe that which has the appearance of truth but might be deceptive. The person or thing that is plausible strikes the superficial judgment favorably; it may or may not be true: a plausible argument (one that cannot be verified or believed in entirely). Specious definitely implies deceit or falsehood; the surface appearances are quite different from what is beneath: a specious pretense of honesty; a specious argument (one deliberately deceptive, probably for selfish or evil purposes).
1540s, "acceptable, agreeable," from L. plausibilis "deserving applause, acceptable," from pp. stem of plaudere "to applaud" (see plaudit). Meaning "having the appearance of truth" is recorded from 1560s.