Origin of laughable?
Laughable Adjective: to inspire laughter: comically ridiculous. A variation based on laugh which evolved from the Middle English laughen, laghen
This is an example of Shakespeare 'remixing' vocabulary. He takes an existing word and creates a new form, adding an extra dimension distinct from the original in the process.
With laughable that dimension is a link the Latin
(1590) - one of Shakespeare's darker comedies. The tone is set in the opening scene.The Merchant of Venice
|The Merchant of Venice 1.1.56
Solanio is teasing his friend Antonio. The classical allusions ('Now, by two-headed Janus') are part of the wit and wordplay that were staples of Elizabethan comedy.
Laughable is now rarely used in the sense of purely inspiring laughter. There is nearly always an element of ridicule: a laughable attempt to explain his lateness.