Since Semantics is the study of meanings of words, you could do:
- Dictionaries
- Some weird word meanings and where they came from
- What we use to find out the meanings of rarely-used words
- Words whose meanings have completely changed over the years.
- Ancient words we still use today
- Words that have completely lost their meanings over the years
- And words that have a weird meaning.
Hope that hepls! Good luck with your presentation!