means A religious discourse delivered from a pulpit, typically expounding on a scriptural text or moral lesson; by extension, any lengthy, earnest, often unwanted lecture.

from From Latin sermo, meaning 'talk, discourse, conversation' — originally something far chattier than the monologue it became. Sermo likely traces back to the root serere, 'to join or string together,' the same image-cluster behind 'series': words linked link by link into a chain. It entered English through Old French sermun around the 12th century, by which time the casual Latin 'conversation' had hardened into the one-way pulpit address we know — the talk where, fittingly, no one talks back.