Analyze the semantic shift of the word 'silly' from its Old English origin (meaning 'happy' or 'blessed') to its modern meaning ('foolish'). Using the principles of historical linguistics, trace the path through Middle English (meaning 'innocent', then 'pitiable', then 'weak'). Compare this trajectory with the phenomenon of 'pejoration' and provide two other examples of English words that have undergone a similar shift from positive to negative connotations over centuries.