bard(RIP) was powered by gemini which was powered by palm2 or something, which was powered by deepmind which was powered by google which was powered by alphabet or sth
2017: Transformers invented
2018: BERT
2020: Meena
2021: LaMDa -> First model Bard was built on
2022: PaLM
2023: PaLM2
Late 2023: Gemini
It probably would have been clearer if they used simple numerical versioning like OpenAI's GPT-{2,3,3.5,3}. I suppose the idea is to do that with Gemini now.
More info here: https://en.wikipedia.org/wiki/Gemini_(chatbot)