The word 肃然起敬 is formed by combining the character 肃 (solemn) with the suffix 然 (meaning 'in a manner') to create the adverb 肃然 (solemnly), which then modifies the verb phrase 起敬, composed of 起 (to arise) and 敬 (respect). This results in a literal meaning of "to arise with respect solemnly", describing the action of becoming deeply respectful.