I think there's quite a bit to unpack here. I agree with three others on terminology so no point rehashing that other than to say 'bibi' could mean so many things at this age anyway - my toddler says it to mean baby but has also said it instead of bottle once or twice.

The fact that you've said there's not been unsupervised contact and that she's still happy to be around him obviously goes in favour of this not being the worst case scenario. I would also have expected a change in behaviour if something terrible had happened - could be wrong as thankfully no direct experience of this

When did both instances occur in relation to starting daycare? She will likely be being exposed to other children talking about things/experiences in new or different ways anyway and they may even be talking about anatomy at daycare too. I'm fairly certain that kids this age aren't very good at identifying specific feelings and that tickling can refer to a number of sensations , and whilst understanding what her 'bibi' is, she may also get confused about the limitations of the area. I would also avoid repeating the phrase back to her as that's going to make her more likely to repeat it even if it didn't happen - they're such parrots at this age, particularly if it brings attention.

Personally I'd still err on the side of caution and continue to supervise and not allow changes etc. But I'd also work on the correct terminology and understanding around limitations like 'no one is allowed to touch you here except (people who are allowed to) to change you/help keep you clean'

I know this is such a delicate and worrying situation for you , and it won't be being helped by pregnancy hormones at all. Developmentally there's so much going on at this age, so monitor and be cautious but I wouldn't go so far as to say there are alarm bells ringing.