Earlier quoted context omitted.
Sharp started out making mechanical pencils. Panasonic started out making lightbulb sockets. Mitsubishi started as a shipping company.
Though I believe all these companies still make these products. They have simply expanded into other sectors.
To your broader point, though, it's true that most of the major Japanese conglomerates have amusing/modest origins and have accrued side-businesses over time until they became goliaths.
It's still interesting that a company like Panasonic began with something so mundane. Other than a few cases like IBM (which began as separate companies making time clocks and card punchers), it's not that common a story in the western market.