Why do historic Celtic regions and tribes have the root "Gal-", "Wal" and "-gal" in their names?

[Sikeliot]

Galicia
Galway
Portugal
Donegal

Gaul
Gaels/Gaelic
Wales
Wallonia

I am sure there are many others.

[Mingle]

Galicia
Portugal

It comes from the Proto-Celtic *gal- which means "to be able".

Two other examples are the words Kelt and Gallia.

Gaels/Gaelic

The word Gael likely has a different etymology from the rest and comes from the Proto-Celtic *wēdelos which means "savage, woodsman".

Gaul

Despite the superficial resemblance, this word is not related to the Latin Gallia. This comes from the same root as Wales and Wallonia which I'll discuss below.

Wales
Wallonia

This comes from the Proto-Germanic word *walhaz which meant "foreigner (non-Germanic)". The Proto-Germanic word likely came from the name Volcae who were a Gaulish tribe.

Other examples include Wallach, Vlach, and Cornwall.

[Albannach]

I always found it interesting that the French call Wales pays de Galles, there definitely seems to be some correlation with Gal and Celt, you can even see it as far away as Turkey with the Galatians.

I know the Gal part of Donegal and is supposed to mean Foreigners/Strangers same with the Gaelic name for the Hebrides, Innse Gall, and Galloway Gall-Ghaidhealaibh.

[Grace O'Malley]

I'm sure others can pipe in on the other names but all of these are not connected.

Donegal in English means Fort of the Foreigners. In Irish: Dún na nGall. Gall in Irish meant foreigner namely Vikings and after that it was Normans or British. Gall is from Old Irish and means foreigner. That's why Vikings were called Dubgaill (dark strangers) and Finngaill (fair strangers). Gaill is the plural of Gall.

Galway comes from the Irish Gaillimhe. Dún Bhun na Gaillimhe ('Fort at the Mouth of the Gaillimh') was constructed in 1124, by the King of Connacht Tairrdelbach Ua Conchobair.

Gael is a name originally borrowed from old Welsh. The Welsh called the Irish Guoidel.

According to the scholar John T. Koch, the Old Irish form of the name, Goídel (also spelled Gaídel), was borrowed from a Primitive Welsh form Guoidel roughly meaning "forest people", "wild men" or, later, "warriors".

https://en.wikipedia.org/wiki/Gaels

[Nurzat]

in Romania: Galați (https://en.wikipedia.org/wiki/Galatians_(people))

[Mens-Sarda]

Other examples include Wallach, Vlach, and Cornwall.

Cornwall comes from Latin Cornu Galliae (Horn of Gaul) that in origin was the name of Brittany, later extended to Cornwall, while Brittany changed name when the Brittonic refugees settled there after the Anglo-Saxon invasion of their lands.

P.S.

Italian town : Senigallia

From Latin Sena Gallica, it could be translated as "Gaulish Senian" = Gaulish of the Senones. The Senones were a celtic tribe who lived in that area

[Sikeliot]

Gael is a name originally borrowed from old Welsh. The Welsh called the Irish Guoidel.

According to the scholar John T. Koch, the Old Irish form of the name, Goídel (also spelled Gaídel), was borrowed from a Primitive Welsh form Guoidel roughly meaning "forest people", "wild men" or, later, "warriors".

This must be why Gaelic languages are also called "Goidelic"

[TheOldNorth]

It comes from the Proto-Celtic *gal- which means "to be able".

Two other examples are the words Kelt and Gallia.



The word Gael likely has a different etymology from the rest and comes from the Proto-Celtic *wēdelos which means "savage, woodsman".



Despite the superficial resemblance, this word is not related to the Latin Gallia. This comes from the same root as Wales and Wallonia which I'll discuss below.



This comes from the Proto-Germanic word *walhaz which meant "foreigner (non-Germanic)". The Proto-Germanic word likely came from the name Volcae who were a Gaulish tribe.

Other examples include Wallach, Vlach, and Cornwall.

proto germanic walhaz comes from the the volcae tribe of Gauls which the name was likely pronounced (wOl-kay)