FromMiddle High Germannist, byform ofnest, fromOld High Germannest, fromProto-Germanic*nestą, fromProto-Indo-European*nisdós. Cognate withGermanNest,Englishnest,Dutchnest. ThroughoutCentral Franconian (and in parts ofRhine Franconian) the underlying Middle High German vowel isi, which regularly yields Luxembourgisha in closed syllables.
Cognate toGermanAst, then resulted from rebracketing after the indefinite article.
Apparently cognate toGermanAst,LuxembourgishAascht (the intrusiven might be a result ofrebracketing, compare e.g.nickname).