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 Latin plausibilis "deserving applause, acceptable," from plaus-, past participle stem of plaudere "to applaud" (see plaudit). Meaning "having the appearance of truth" is recorded from 1560s. Related: Plausibly.