A Babylonish dialect
Which learned pedants much affect.

These lines mock the deliberately obscure, jargon-laden language that “learned pedants” cultivate to signal erudition rather than to communicate. Calling it a “Babylonish dialect” invokes the biblical image of Babel—confusion of tongues—suggesting that such academic or scholastic speech is a kind of self-inflicted linguistic chaos. Butler’s satiric point is that pretentious diction can become a barrier between knowledge and understanding, turning learning into performance and excluding ordinary readers. The couplet’s brisk rhythm and pointed rhyme sharpen the ridicule: the dialect is not an accidental byproduct of learning, but something pedants actively “affect,” i.e., adopt as a pose.