The Welsh Name History
It appears that the name Welsh is from the AngloSaxon word wilisc
meaning Foreigner or 'nonAngloSaxon'.
The Old High German walh became Walch in Middle High German
and walhisk became Mid High German Welsch.
In present day German, Welsche refers to Latin peoples
and the French and the Romanic neighbours of the German speaking lands.

In the case of the British Isles, the AngloSaxon variant wilisc
is applied to the British peoples encountered by the Saxon invaders
and settlers during the 400s & 500s AD.
Over the centuries, the term wilisc evolved through Middle English
into Welsh, referring to outsiders.
Read More: Welsh