'sermonizer' originates from English, specifically the verb 'sermonize', where 'sermon' meant 'a religious discourse' and the suffix '-ize' meant 'to make or perform (an action)'.

'sermonizer' changed from the verb 'sermonize' (formed from 'sermon' + '-ize') with the agentive suffix '-er' to denote 'one who sermonizes', and eventually became the noun 'sermonizer' in modern English.

Initially it meant 'one who gives sermons (religious talks)', but over time it also gained the additional (often pejorative) meaning 'one who moralizes or lectures at tedious length'.