in + let

Inlet is a compound of 'in' and 'let' — the place where water is let in, or the place where it lets itself in. The word first appears in written English around 1570, during the Elizabethan period of intense coastal mapping and navigation. English cartographers needed a word for small waterways that penetrated inland from the coast, and they built one from native parts rather than borrowing from Latin or French.

The simplicity of the word is unusual in English geographic vocabulary. Most coastal terms come from other languages: bay from French, fjord from Norse, cove from Old English, estuary from Latin. Inlet is transparently English — any speaker can hear the meaning in the parts. It is the place where water goes in. The directness is almost suspicious in a language that usually prefers borrowed sophistication.

Alaska has more inlets than any other US state, and they shaped its human geography. Cook Inlet, named for Captain James Cook in 1778, is the waterway on which Anchorage sits. The Tlingit, Haida, and other indigenous peoples of the Pacific Northwest coast lived on and by inlets for thousands of years before European names were applied to them. An inlet provided sheltered water, access to salmon runs, and protection from open-ocean storms.

The word also has a mechanical meaning: an inlet valve, an air inlet, a fuel inlet. This is the same word — an opening where something is let in. The geographic and mechanical meanings are parallel, not metaphorical. Both describe a passage that allows something to enter. Water enters a coastal inlet. Air enters an engine inlet. The letting-in is literal in both cases.