When one thing bumps into another, that’s a “collision.” The that comes from the Latin “collidere,” which was formed from “col” (together) and “laedere” (to hurt by hitting). “Collision” showed up in English in the 1400s, and it’s been in constant use ever since.
Except in one very specific case. When a ship (and only a ship) hits something that’s not another ship — that is, if it bangs into a rock or a bridge, anything that’s not moving — and it happens in the US — and there’s an official, legal report produced about the incident — it’s not a “collision,” it’s an “allision.” Here’s an example from 2013:
“The second case involved a docking pilot in a New England port who allided with a railroad bridge and failed to report the incident to the Coast Guard. Sadly, but not all that rare, the pilot was provided with faulty draft information regarding the vessel he was piloting leading to the allision.”
“Allision” also comes from Latin. It’s from “allisio,” which meant “the act of striking upon.” It arrived in English a couple of centuries later than “collision,” and originally meant exactly the same thing: “Some [sounds] are made by allision, as when the ayre moued by a vehement winde doth beate against a solide body.” (1615). It was never as commonly used as “collision,” but the two words were interchangeable up until about 1867. That’s when an Admiral Smyth of the British Navy pointed out that “Synonymous in marine law with collision, though the jurists of Holland introduce it to mark a distinction between one vessel running against another and two vessels striking each other.”
A few decades after that (but probably not because of it), “allision” had pretty much disappeared from any use other than discussions of seagoing fender-benders. After that it mostly disappeared from even that usage, except in the US, where it was written into maritime law. In that context, it was made legally quite clear that if two ships run into each other, that’s a “collision,” but if one ship bumps violently into something that’s not mobile, then what you have is an “allision.”
If and when you find yourself suddenly forced to steer a 500-foot freighter around a rocky harbor, you may be glad you found out about this. Otherwise, feel free to unread this piece.
