canal

Borrowed from Middle French canal, from Old French canal, from Latin canālis ("channel, canal, narrow passage"), itself from canna ("reed, cane"). That word traces back through Ancient Greek κάννα (kánna, "reed") to Akkadian qanû, also meaning "reed".

The sense moved from the plant itself to the tube-like shape of the reed, then to any hollow channel or passage, and finally settled on the dug waterways we call canals today.

It's a doublet of channel, meaning the two words descend from the same Latin root but arrived in English by different paths. It's also related to cane, which comes from the same reed word.