I think we have like 5 words left from Gaul in modern french (only one I know is 'talus'). Old central French was mostly vulgar latin+frankish, with a bit of Gaulish and Arabic, then Gaulish was traded for latin and greek forcibly thanks to the french 'Academie' that made central/Parisian french the only french, and we lost a lot (a _lot_) of words. What's funny is that English, beside Normand french, borrowed a lot from French before that,and we borrowed those words back, with a different meaning, or sometimes a similar one.