From Old High German arbeit, from Proto-Germanic *arbaidiz. As to the consonantism: Most dialects of Luxembourgish regularly reduced original -cht to -t, but this development was later reverted, probably under outside influences. (The same happened in many dialects of Central Franconian.) Both southernmost and northernmost Luxembourgish often retain forms without -ch-; compare Nuet alongside Nuecht (“night”). In those dialects where the development was reverted, hypercorrect forms with unetymological -ch- occur (compare also attested Jesuiicht for Jesuit).
Aarbecht f (plural Aarbechten)