tombolo

tombolo (TOM-buh-loh) - n., a sand or gravel bar connecting an island to the mainland (or to another island).


And not, as I was vaguely guessing, anything to do with a grave mound -- though tumulus is a doublet. From Italian tombolo, pillow, from Latin tumulus, mound, from tumeō, I swell. Here's one connecting St Ninian's Isle with the Shetland Mainland:


Thanks, WikiMedia!

---L.