Babies learn words from books
This won't be news: children learn more words when you read to them as babies
You can read the research, which was done by the School of Language, Literacy & Early Childhood Education in Dublin City University’s Institute of Education and the University of North Carolina:
Three-year-olds have a wider vocabulary if they are read to as babies (daynurseries.co.uk)
or you can go straight to the library: