the word 'suddenly' is formed from the adjective 'sudden' and the adverbial suffix '-ly'. the core adjective 'sudden' entered english via old french from the late latin 'subitāneus', meaning 'sudden'. this, in turn, derives from the classical latin 'subitus', meaning 'sudden' or 'unexpected', which is the past participle of 'subīre', meaning 'to come or go up stealthily'. the verb 'subīre' itself is a compound of 'sub-' (from below, secretly) and 'īre' (to go), painting a vivid picture of something arising stealthily from below, hence without warning. the suffix '-ly' has germanic origins, evolving from the old english '-līċe', used to form adverbs from adjectives, thus transforming the quality of being unexpected into the manner of occurring in an unexpected way.

Structure: sudden (unexpected) + ly (adverb suffix) - sudden: from middle english 'sodein', from old french 'sodain', from late latin 'subitāneus' (sudden), from latin 'subitus' (sudden, unexpected). functions as the adjective root. - ly: from old english '-līċe' (adverb-forming suffix). functions as a suffix forming adverbs from adjectives.