From Greek 'dokein' (to think, to seem) — originally a neutral opinion or decree, turned pejorative by the Enlightenment.
A principle or set of principles laid down by an authority as incontrovertibly true; a belief held rigidly and without question.
From Latin 'dogma' (philosophical tenet), from Greek 'dogma' (opinion, tenet, decree), from 'dokein' (to seem, to think, to suppose), from Proto-Indo-European '*deḱ-' (to take, to accept). The same root 'dokein' underlies 'paradox' and 'orthodox.' In Greek, a 'dogma' was simply an opinion or a decree — it carried no negative connotation. The pejorative sense of rigid, unquestioned belief developed in English during the Enlightenment, when reason was contrasted with received authority
Despite appearances, 'dogma' has nothing to do with dogs. The Greek root 'dokein' (to think) connects 'dogma' to 'doctor' (from Latin 'docēre,' to teach, from the same PIE root '*deḱ-'). A dogma is 'what is thought to be true,' a doctor is 'one who teaches,' and a doctrine is 'what is taught' — all from the same ancient root meaning 'to accept.'