When I first looked this up, I felt a bit stupid, as my idea of what the word meant (something like lagoon, oasis or watery landscape) was so different from its actual meaning (a blank space or missing part). In the context, it referred particularly to a gap in a manuscript.

I find it quite shocking, after having worked with language for so many years, that there are still words I can be so wrong about. But bear with me, because it turns out there is a connection. Phew.

First, the definitions.

• Oxford: an unfilled space; a gap; (anatomy) a cavity or depression, especially in bone.
• Collins: a gap or space, esp in a book or manuscript; (biology) a cavity or depression, such as any of the spaces in the matrix of bone; another name for coffer (in the sense of an ornamental sunken panel).

I still had this tugging feeling of a connection with water, and I wondered if I was just getting confused because ‘lacuna’ and ‘lagoon’ sound similar. As ever, Etymonline came to the rescue. Indeed, both words stem from the Latin lacuna meaning hole or pit, and lacus, meaning pond or lake.

In fact, ‘lagoon’ (meaning a pond or channel near to a larger body of water) developed in the 1670s, coming out of the earlier version ‘laguna’, which is first recorded in the 1610s.

So there we go. Not quite mad, yet.